Britain's Prince Charles waves as he leaves the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles waves as he leaves the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles and GCHQ Director Jeremy Fleming react as they watch the RAF Red Arrow display team at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles and GCHQ Director Jeremy Fleming react as they watch the RAF Red Arrow display team at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles reacts next to GCHQ Director Jeremy Fleming after planting a tree in front of the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles reacts next to GCHQ Director Jeremy Fleming after planting a tree in front of the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles reacts next to GCHQ Director Jeremy Fleming after planting a tree in front of the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles and GCHQ Director Jeremy Fleming watch the RAF Red Arrow display team at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles signature is pictured in the visitors book in the museum area of the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles signs the visitors book in the museum area of the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles talks with the GCHQ Historian Tony Comer at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles talks with the GCHQ Historian Tony Comer at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles talks with the GCHQ Historian Tony Comer at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles gestures after addressing the staff at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles gestures after addressing the staff at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles addresses the staff at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles addresses the staff at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles looks on before speaking with staff at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles gestures before speaking with staff at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles gestures before speaking with staff at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles gestures before speaking with staff at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles talks with GCHQ Director Jeremy Fleming as he visits the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles walks with GCHQ Director Jeremy Fleming as he visits the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles talks with GCHQ Director Jeremy Fleming as he visits the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles talks with GCHQ Director Jeremy Fleming as he visits the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles talks with GCHQ Director Jeremy Fleming as he visits the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles talks with GCHQ Director Jeremy Fleming as he visits the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles arrives at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles arrives at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles arrives at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles talks with GCHQ Director Jeremy Fleming as he arrives at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles arrives at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

Britain's Prince Charles arrives at the GCHQ headquarters in Cheltenham, Britain July 12, 2019. REUTERS/Peter Nicholls

The former headquarters of Intelligence, Cyber and Security Agency GCHQ, is seen in Palmer Street, after the agency revealed the location, following its departure to new undisclosed offices, in London, Britain April 4, 2019. Picture taken April 4, 2019. REUTERS/Henry Nicholls

The former headquarters of Intelligence, Cyber and Security Agency GCHQ, is seen in Palmer Street, after the agency revealed the location, following its departure to new undisclosed offices, in London, Britain April 4, 2019. Picture taken April 4, 2019. REUTERS/Henry Nicholls

The former headquarters of Intelligence, Cyber and Security Agency GCHQ, is seen in Palmer Street, after the agency revealed the location, following its departure to new undisclosed offices, in London, Britain April 4, 2019. Picture taken April 4, 2019. REUTERS/Henry Nicholls

The former headquarters of Intelligence, Cyber and Security Agency GCHQ, is seen in Palmer Street, after the agency revealed the location, following its departure to new undisclosed offices, in London, Britain April 4, 2019. Picture taken April 4, 2019. REUTERS/Henry Nicholls

The former headquarters of Intelligence, Cyber and Security Agency GCHQ, is seen in Palmer Street, after the agency revealed the location, following its departure to new undisclosed offices, in London, Britain April 4, 2019. Picture taken April 4, 2019. REUTERS/Henry Nicholls

The former headquarters of Intelligence, Cyber and Security Agency GCHQ, is seen in Palmer Street, after the agency revealed the location, following its departure to new undisclosed offices, in London, Britain April 4, 2019. Picture taken April 4, 2019. REUTERS/Henry Nicholls

The former headquarters of Intelligence, Cyber and Security Agency GCHQ, is seen in Palmer Street, after the agency revealed the location, following its departure to new undisclosed offices, in London, Britain April 4, 2019. Picture taken April 4, 2019. REUTERS/Henry Nicholls

The former headquarters of Intelligence, Cyber and Security Agency GCHQ, is seen in Palmer Street, after the agency revealed the location, following its departure to new undisclosed offices, in London, Britain April 4, 2019. Picture taken April 4, 2019. REUTERS/Henry Nicholls

The former headquarters of Intelligence, Cyber and Security Agency GCHQ, is seen in Palmer Street, after the agency revealed the location, following its departure to new undisclosed offices, in London, Britain April 4, 2019. Picture taken April 4, 2019. REUTERS/Henry Nicholls

The former headquarters of Intelligence, Cyber and Security Agency GCHQ, is seen in Palmer Street, after the agency revealed the location, following its departure to new undisclosed offices, in London, Britain April 4, 2019. Picture taken April 4, 2019. REUTERS/Henry Nicholls

A GCHQ plaque is seen during Britain's Queen Elizabeth's visit at the Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth shakes hands with Bletchley Park veteran Ruth Bourne during her visit at the Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth looks at artefacts as she meets with GCHQ Director Jeremy Fleming and historian Tony Comer during her visit at the Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth meets with GCHQ Director Jeremy Fleming as she visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth listens to GCHQ Director Jeremy Fleming as she visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth receives a bouquet of flowers as she visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth listens to GCHQ Director Jeremy Fleming as she visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool

Britain's Queen Elizabeth meets with GCHQ Director Jeremy Fleming as she visits Watergate House to mark the centenary of the GCHQ (Government Communications Head Quarters) in London, Britain, February 14, 2019. REUTERS/Hannah McKay/Pool