We had to act on Pope death plot fear says Met after cleaners are freed

Five of the men were seized by armed officers at a Westminster street cleaning depot before dawn on Friday after police received information about a threat to Benedict XVI. A sixth was arrested at his north London home.

The cleaners, all of North African origin, were released over the weekend after counter terrorist detectives found no evidence to support the suspicions.

Officers searched their Chiltern Street depot as well as a number of homes in east and north London but no weapons or suspicious materials were found.

It emerged that the suspects were reported to police by a colleague who overheard them joking in the work canteen about how to kill the Pope.

One reportedly said: "It'd be pretty difficult to shoot the Pope, wouldn't it, as his car is bullet-proof." Another apparently replied: "Yeah but I bet an RPG (rocket-propelled grenade) would get through easily enough."

Scotland Yard sources said they were passed information which they had only hours to check out before the Pope was due to tour the streets of Westminster in a motorcade.

One said: "The initial information was treated seriously and we started checking it. There were issues which gave us some cause for concern.

"It is a difficult balance but safety is our paramount concern. We had only a few hours to make a judgment and a decision was taken to arrest them so we could check the information properly.

"Hindsight is a great thing but what would people have said if we had not acted and something happened."

The six men arrested were aged 26, 27, 29, 36, 40 and 50. They all worked for Veolia Environmental Services, a contractor which employs 650 staff to keep Westminster's streets clean. A council spokesman said they were expected to return to work this week.

There is concern among senior officers that the men could take legal action against the Met for unlawful arrest and detention. For a legal action to succeed they will have to prove that the actions of the anti-terrorist officers were disproportionate and ill-informed.

London's Roman Catholics today hailed the Pope's three-day visit to the capital as a success.

Father John Docherty was among the priests who attended the pontiff's visit to St Peter's, a residential home run by nuns for the elderly in Vauxhall, on Saturday.

He said: "Some of the people in the home are in their nineties and can't get down the stairs, so the Pope went upstairs to see them.

"He talked about how caring for the elderly is not simply generosity on our part, it's our duty. I think that everyone was impressed by his wisdom and sincerity.

Father Docherty, priest of St Anne's Church in Kennington, added that he hoped even non-religious Londoners appreciated the Pope's apologies over the child sexual abuse cases.