BBC had 'secret security switch'

"Three or four people" could hijack the BBC's HQ, Reith warned

A secret cut-off switch was installed in the BBC's Broadcasting House in the 1930s to prevent any unauthorised access, documents have revealed.

BBC director general Sir John Reith ordered its installation in 1934, files released by the National Archives show.

He was concerned at the potential ease with which political extremists or even student pranksters could enter the London building and broadcast.

Bullet-proof shutters were also installed as a security measure.

'Highly undesirable'

The shutters could be instantly lowered in an emergency and two guards at the main entrance had orders not to allow any unauthorised persons to enter.

The measures came after Sir John warned in a memo: "Today it is quite obvious that three or four people could walk in and hold up the entire building, particularly in the evening.

"Such an occurrence (is) highly undesirable, even if it were simply a hoax on the part of a band of students."