Londoners prayed, laid wreaths and observed a two-minute silence in remembrance of the victims of the terrorist bombings last year that killed 52 innocent people and injured hundreds.
The Queen, Tony Blair, and Ken Livingstone, mayor of London, led tributes to the dead, while senior police warned the country not to lower its guard against the threat of further attack.
Sir Ian Blair, commissioner of the Metropolitan police, said: “No matter how dreadful the terrorists are, it is infinitesimal compared to the strength of Londoners.”
The most senior policeman told the BBC he had no doubt there would be further attacks, and the security services were doing all they could to prevent them.
Police said this week they were investigating an uprecedented number of plots and had thwarted at least three attacks since last July.
But Sir Ian spoke amid continuing gaps in firm intelligence and government concerns that some suspects had escaped the intensified surveillance and disruption operations led by MI5, the Security Service.
Sir Ian said: “It is not the police or the intelligence services that will defeat the terrorists. It is the communities. They must be our eyes and ears on the streets and tell us about their concerns.”
In the morning, memorial plaques were unveiled in the presence of relatives of the dead and survivors at each of the sites where bombs were detonated. Three went off on the London Underground and a fourth on a double-decker bus.
At midday, offices, shops and public transport fell silent as people reflected on the memory of the worst terrorist attack on the capital.
In the afternoon, government ministers as well as opposition party leaders attended a ceremony of remembrance in London’s Regent’s Park.
The highest-profile event of the day was the creation of a giant tribute in the shape of the figure seven and filled with carnations. As the tribute took shape, the London Gospel Choir sang “Something Inside So Strong”, “Lean on Me” and “Bridge Over Troubled Waters”.
Earlier in the day, the prime minister marked the two-minute silence at the London Fire Brigade headquarters in Lambeth, south London. In a statement he called on the community to unite against terrorism.
However, the release on Thursday of a videotaped statement made by one of the bombers before last July’s attack has focused the mind of the government on the challenges it faces in the days ahead.
In the tape aired on Qatar-based al-Jazeera television, Shehzad Tanweer, 22, warned of a further violence until UK troops pulled out of Iraq and Afghanistan.
While opinion polls show that a majority of British Muslims are against terrorism, they also show that even moderate members of the community blame British foreign policy for fuelling extremism.