An assistant poses with Britain's Princess Diana's Victor Edelstein midnight-blue velvet evening gown (estimated at £250,000 - £350,000), which was worn by the princess when she danced with actor John Travolta at the White House in 1985. Also pictured is her Katherine Cusack evening gown (estimated at £20,000 -£30,000) and her Catherine Walker dress (estimated £4,000 - £6,000), at Kerry Taylor auctions in London, Britain December 8, 2019. REUTERS/Henry Nicholls

An assistant poses with Britain's Princess Diana's Victor Edelstein midnight-blue velvet evening gown (estimated at £250,000 - £350,000), which was worn by the princess when she danced with actor John Travolta at the White House in 1985. Also pictured is her Katherine Cusack evening gown (estimated at £20,000 -£30,000) and her Catherine Walker dress (estimated £4,000 - £6,000), at Kerry Taylor auctions in London, Britain December 8, 2019. REUTERS/Henry Nicholls

An assistant poses with Britain's Princess Diana's Victor Edelstein midnight-blue velvet evening gown (estimated at £250,000 - £350,000), which was worn by the princess when she danced with actor John Travolta at the White House in 1985. Also pictured is her Katherine Cusack evening gown (estimated at £20,000 -£30,000) and her Catherine Walker dress (estimated £4,000 - £6,000), at Kerry Taylor auctions in London, Britain December 8, 2019. REUTERS/Henry Nicholls

An assistant poses with Britain's Princess Diana's Victor Edelstein midnight-blue velvet evening gown (estimated at £250,000 - £350,000), which was worn by the princess when she danced with actor John Travolta at the White House in 1985. Also pictured is her Katherine Cusack evening gown (estimated at £20,000 -£30,000) and her Catherine Walker dress (estimated £4,000 - £6,000), at Kerry Taylor auctions in London, Britain December 8, 2019. REUTERS/Henry Nicholls

An assistant poses with Britain's Princess Diana's Victor Edelstein midnight-blue velvet evening gown (estimated at £250,000 - £350,000), which was worn by the princess when she danced with actor John Travolta at the White House in 1985. Also pictured is her Katherine Cusack evening gown (estimated at £20,000 -£30,000) and her Catherine Walker dress (estimated £4,000 - £6,000), at Kerry Taylor auctions in London, Britain December 8, 2019. REUTERS/Henry Nicholls

An assistant poses with Britain's Princess Diana's Victor Edelstein midnight-blue velvet evening gown (estimated at £250,000 - £350,000), which was worn by the princess when she danced with actor John Travolta at the White House in 1985. Also pictured is her Katherine Cusack evening gown (estimated at £20,000 -£30,000) and her Catherine Walker dress (estimated £4,000 - £6,000), at Kerry Taylor auctions in London, Britain December 8, 2019. REUTERS/Henry Nicholls

Britain's Princess Diana's Victor Edelstein midnight-blue velvet evening gown (estimated at £250,000 - £350,000), which was worn by the princess when she danced with actor John Travolta at the White House in 1985. Also pictured is her Katherine Cusack evening gown (estimated at £20,000 -£30,000) and her Catherine Walker dress (estimated £4,000 - £6,000), displayed at Kerry Taylor auctions in London, Britain December 8, 2019. REUTERS/Henry Nicholls

Britain's Princess Diana's Victor Edelstein midnight-blue velvet evening gown (estimated at £250,000 - £350,000), which was worn by the princess when she danced with actor John Travolta at the White House in 1985. Also pictured is her Katherine Cusack evening gown (estimated at £20,000 -£30,000) and her Catherine Walker dress (estimated £4,000 - £6,000), displayed at Kerry Taylor auctions in London, Britain December 8, 2019. REUTERS/Henry Nicholls

A blue velvet nudibranch crawls on the sand in front of a large sea cucumber in the Great Barrier Reef off the coast of Cairns, Australia October 26, 2019. REUTERS/Lucas Jackson

People lit candles during a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

People lit candles during a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Peopleare seen by candles during a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Peopleare seen by candles during a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Peopleare seen by candles during a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

People light candles during a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

People look at candle lights during a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

A woman waves a flag of Czech Republic during a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

People hold flags of Czech Republic on top of a building during a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

People hold flags of Czech Republic on top of a building during a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

People attend a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

General view of people attending a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

People attend a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

People attend a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

People attend a reenactment of the 1989 protest march to commemorate the 30th anniversary of the 1989 Velvet Revolution in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Slovakia's Prime Minister Peter Pellegrini speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Slovakia's Prime Minister Peter Pellegrini speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Hungary's Prime Minister Viktor Orban speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

President of the German Bundestag Wolfgang Schaeuble speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Hungary's Prime Minister Viktor Orban speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Poland's Prime Minister Mateusz Morawiecki speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Poland's Prime Minister Mateusz Morawiecki speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

President of the German Bundestag Wolfgang Schaeuble speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Czech Prime Minister Andrej Babis speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

General view of the venue before a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Czech Prime Minister Andrej Babis speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Czech Prime Minister Andrej Babis speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Czech Prime Minister Andrej Babis speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Czech Prime Minister Andrej Babis speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Czech Prime Minister Andrej Babis speaks during a ceremony marking the 30th anniversary of the 1989 Velvet Revolution at the National Museum in Prague, Czech Republic, November 17, 2019. REUTERS/David W Cerny

Demonstrators cast shadows at an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators hold signs at an anti-government protest, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators hold signs at an anti-government protest, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators hold signs at an anti-government protest, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators wave Czech flags as others below gather at an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

A woman waves the Czech flag as demonstrators attend an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators attend an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators wave Czech flags during an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

A man waves the Czech flag as demonstrators attend an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators wave Czech flags as others gather below for an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators wave Czech flags during an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators wave Czech flags from the top of a building during an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators wave Czech flags as others gather below for an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators attend an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

A man waves the Czech flag as demonstrators attend an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators attend an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators attend an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators attend an anti-government rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators attend an anti-government protest rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators attend an anti-government protest rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny

Demonstrators attend an anti-government protest rally, organised by Million Moments for Democracy, a day ahead of the 30th anniversary of the 1989 Velvet Revolution that led to the fall of Communism in former Czechoslovakia, in Prague, Czech Republic November 16, 2019. REUTERS/David W Cerny