For decades the BBC denied that job applicants were subject to political vetting by MI5. But in fact vetting began in the early days of the BBC and continued until the 1990s.
Paul Reynolds, the first journalist to see all the BBC's vetting files, tells the story of the long relationship between the corporation and the Security Service.
As early as 1933 a BBC executive, Col Alan Dawnay, had begun holding meetings to exchange information with the head of MI5, Sir Vernon Kell, at Dawnay's flat in Eaton Terrace, Chelsea.
It was an era of political radicalism and both sides deemed the BBC in need of “assistance in regard to communist activities”.
“Formalities” was the code word for the vetting system
And so routine vetting began. From the start, the BBC undertook not to reveal the role of the Security Service (MI5), or the fact of vetting itself.
On one level this made sense, bearing in mind that the very existence of the Secret Service remained a secret until the 1989 Security Service Act.
A memo from 1984 gives a run-down of organisations on the banned list.
On the left, there were the Communist Party of Great Britain, the Socialist Workers Party, the Workers Revolutionary Party and the Militant Tendency.
By this stage there were also concerns about movements on the right - the National Front and the British National Party.
A banned applicant did not need to be a member of these organisations - association was enough.
If staff came under suspicion only after they had been employed by the BBC or applied for transfer to a job that needed vetting, an image resembling a Christmas tree was drawn on their personal file.
The satirical show That Was The Week helped cement Hugh Greene's reputation as a liberaliser.
Arkell suggests that the BBC can get credit from MI5 for his performance under “penetrating” questioning from the Sunday Times
Banned applicants did not know why they had been turned down, though they might have guessed.
Another candidate who was rejected on MI5's advice was Tom Archer, who worked as a BBC freelancer in Bristol in the 1970s, but was turned down when he applied for staff jobs from 1979 onwards.
Archer was being blocked because a close relative had allegedly joined the Socialist Workers Party.
The BBC files on vetting have themselves been vetted to remove the names of MI5 staff
The vetting files at the BBC's Written Archives in Caversham
BBC correspondents, such as Paul Reynolds, remained subject to vetting even after 1985
Then, two years later, the wartime broadcasting system was stood down, so vetting was further cut back.
The BBC will not say whether any staff are vetted these days.
“We do not comment on security issues,” a spokesperson said.
But any residual vetting, of people needing access to classified information for emergency planning for example, would be open and known to the person.
There is no more secrecy as once there was.