Police have arrested the protester who threw green custard at the openly gay Business Secretary Peter Mandelson. He this morning expressed his surprise that the protester “could just sort of saunter off without being apprehended.”

Leila Deen, from the group Plane Stupid, which is campaigning against expansion of Heathrow airport, threw the coffee cup of green custard over him, covering his face and jacket.

Ms Deen, of Brighton, has been bailed to return at a police station in April.

The attack happened as the gay politician was leaving the government’s low carbon industrial strategy meeting at the Royal Society in London.

Lord Mandelson, this week named the most powerful gay person in Britain, told Andrew Marr on the BBC’s Sunday AM: “very unpleasant it was too.”

Asked how he cleaned himself up so quickly, Lord Mandelson replied: “Same suit, different tie, brilliant young Private Secretary, tie to the fore. New tie to the fore.”

Questioned about how the protester was able to gain access to him so quickly, the Business Secretary replied: “It could have been something nastier and it did actually leave a slight sort of irritation on my face. But I mean not only was I slightly surprised that she could just sort of saunter off without being apprehended. I was also slightly disappointed that some in the media just took her into their studios and started interviewing her, which is I think an advertisement you know for…”

Mr Marr interrupted him saying: “Well you’re a former Northern Ireland Secretary. I mean it’s quite surprising that somebody could walk straight up to you.”

“A bit surprising,” Lord Mandelson responded. “I mean, look, you know we live in a… We don’t live in a police state in Britain, and thank goodness for it. I mean you know there are security measures where people need them. I used to have twenty-four hour permanent security. I would on balance prefer not to go back to those days. But you know, look, I’m not going to comment on this further. This is a matter for the police and the personal protection folk, not me.”