A day of remembrance for the 52 innocent people killed when four suicide bombers detonated their explosives on London transport a year ago culminated tonight with a memorial service in Regent's Park.

The simple ceremony, in the serene surroundings of Queen Mary’s Gardens, began with a powerful rendition of Something Inside So Strong, sung by the London Community Gospel Choir.

Bereaved relatives gave speeches and readings before an audience of more than 1,000 people. Scores more watched from behind barriers erected at the back of the arena.

Tony Blair and his wife, Cherie, sat to the right of the stage alongside the leaders of the other main political parties, David Cameron and Sir Menzies Campbell. John Reid, the Home Secretary, and Ken Livingstone, the Mayor of London, sat nearby.

Throughout the day, wellwishers laid flowers at a giant floral tribute to the victims in the park. The tribute, which is 40 feet across, is in the shape of a flower with seven petals, each filled with purple carnations.

Survivors and relatives came forward and placed yellow gerberas at the centre of the flower at the conclusion of tonight's memorial service.

At noon, millions of Britons observed two minutes’ silence to mark the first anniversary of the attacks of July 7, when four young British Muslims killed 52 innocent people in the country's first suicide bombings.

Thousands of London commuters passing through or past transport landmarks that will forever be associated with Britain's worst terrorist outrage stopped to pay their respects.

The official commemorations began this morning with a simple ceremony at King's Cross station, under which at 8.50am one year ago Jermaine Lindsay, a Jamaican-born Muslim convert, detonated his rucksack device on a train to Russell Square, killing 26 people.

A year to the minute after that attack, Tessa Jowell, the Culture Secretary, and Mr Livingstone laid wreaths in tribute to the dead, joined by relatives of those killed in the blast. The Mayor's message read: "London will never forget those we lost on July 7 2005 and we will build a better city as the best way of remembering them."

Also laying a tribute was Nader Mozakka, who lost his wife Behnaz in the King’s Cross bombing.

"I said goodbye to my wife at 7am a year ago and never saw her again," said Mr Mozakka, 50, from North Finchley, north-west London. "It was tortuous for me to sit in a train today and it was tortuous for me to come here to King’s Cross."

After low-key but poignant ceremonies at the site of the four July 7 attacks, the commemorations include a national two-minute silence started by the chimes of Big Ben and observed in shops, factories and offices across the country.

At the four blast sites, thousands of commuters, survivors and relatives of the victims stood solemnly, many with their heads bowed. The silence was also observed at the Wimbledon tennis tournament and by the Queen and other members of the Royal Family at a service in Edinburgh.

Mr Blair observed the silence with members of the emergency services who led the response to the bombings. In a statement released by his office, the Prime Minister said: "This is a time when our country unites across all races, religions and divides and stands in solidarity with all those who have suffered so much in sympathy with them and in defence of the values we share."

Londoners were still celebrating their surprise win over Paris in the contest to host the 2012 Olympics when the four bombers arrived at King’s Cross on the Thameslink service from Luton one year ago and then fanned out across the capital on their mission of death.

Lindsay, Mohammad Sidique Khan and Shehzad Tanweer exploded their bombs at almost exactly the same time, bringing carnage to the Underground. Hasib Hussain, at 18 the youngest of the bombers, detonated his device just under an hour later, ripping apart a double-decker bus in Tavistock Square.

After ceremonies at the scenes of all the blasts, memorial plaques were unveiled at five locations across London later this morning: Tavistock Square, Aldgate station, where Tanweer detonated his bomb, Edgware Road, where Khan detonated his, and at King’s Cross and Russell Square stations - between which Lindsay exploded his device. All listed the names of those killed at the various sites.

Despite the grief, the prevailing mood on the streets of London was one of pragmatism, allied with the same sense of togetherness that saw the city unite after Britain's first suicide terror attacks.

"You can't think about it, you just have to get on with your day," said Richard Wallis, an IT worker, as he walked past King's Cross station. "I suppose it's in people's minds with the video last night (of Shehzad Tanweer), but it should be a day for the families and the survivors."

A year on from the attacks, Sir Ian Blair, the Metropolitan Police Commissioner, said that the threat of further terrorist attacks had "palpably increased" and the possibility of another attack was "very real".

"Since July the threat has palpably increased and I fear that we have to accept that we live in an age for some years when the threat of an attack getting through is very real," Sir Ian told BBC Radio 4's Today programme. "The threat is very grim, there is no doubt about it. There are, as we speak, people in the United Kingdom planning further atrocities."

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