The former police chief who controversially arrested a Tory MP in a Home Office leaks probe has defended his actions.
Bob Quick, whose detention of Damian Green sparked a storm of parliamentary protest, said he had to act after discovering documents had been stolen from the Home Secretary's safe.
In a BBC interview, the former Metropolitan Police assistant commissioner said: "What we didn't know is whether more serious offences had been committed.
"All we really knew was that someone or maybe more than one person was prepared to steal documents from the Home Secretary's private office safe and intercept her letters to the Prime Minister...so for these reasons we saw it as pretty serious."
He added: "I think this point got lost in the furore about violating the sanctity of Parliament. In that noise it was very difficult to convey the facts.
"The difficulty really was that if you have someone that you can clearly demonstrate was prepared to steal documents from a safe that we know holds very sensitive material, then you're under a duty to find out exactly what has been leaked and to whom."
Mr Quick's team also arrested civil servant Christopher Galley as part of the probe into leaks from the office of then-Home Secretary Jacqui Smith.
The officer was the national co-ordinator of counter-terrorism at the time, and began investigating amid fears of a potential breach of national security.
His officers raided Mr Green's Commons office too, an event captured on camera and broadcast on news outlets.
Neither the MP, who was the then-Tories' immigration spokesman, nor the official ended up being charged.
Mr Quick was criticised for the policing operation, and stepped down in April last year after accidentally showing off secret documents as he arrived for a meeting in Downing Street.
He suggested he may have survived that gaffe had it not been for the leaks probe.
"I accepted I wasn't popular in those quarters," the officer told the BBC.
"I'd read in newspapers various unattributed comments - 'we're going to get Quick' and all this sort of nonsense - so I guess I wasn't surprised by that."
Mr Green's arrest in November 2008 was described as disproportionate in a report by the Inspectorate of Constabulary.
Another review of the affair by a senior officer also said the leaked material amounted only to "embarrassment matters" for the Government and not information of national security.