A day-long series of prayers and commemorative events has been planned to pay tribute to those who lost their lives, including the reading aloud of every victim's name at what is expected to be a poignant memorial service.
Threat 'palpably increased'
Meanwhile the head of London’s police force, Sir Ian Blair, says the threat of more terrorist attacks on British soil has "palpably increased" since the bombings.
The commissioner of the Metropolitan Police, told BBC radio that the threats were both domestic and foreign, and that "there will be more raids" to stop suspected plots.
"Since July 7, the threat has palpably increased," Blair said. "I fear we have to accept that we live in an age ... when the threat of an attack getting through is very real."
He said three "serious conspiracies ... from outside and inside" had been interdicted over the past 12 months, and that 60 suspected terrorists have been charged or are awaiting trial.
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London Mayor Ken Livingstone, Culture Secretary Tessa Jowell and the British capital's Transport Commissioner Peter Hendy begin the tributes by laying flowers at King's Cross station at 8:50 am London time.
The timing coincides with the first of three explosions on London Underground trains; the location reflects where the home-grown Islamic extremist bombers arrived by train and parted on their brief, but deadly, campaign of terror.
More flowers will then be laid at Tavistock Square at 9:47 am, the exact time Hasib Hussain detonated the fourth bomb on a packed number 30 double-decker bus as commuters sought to avoid the unfurling chaos underground.
At 11:30 am, memorial plaques will be unveiled at five locations: Tavistock Square; Aldgate station, where Shehzad Tanweer detonated his bomb; Edgware Road station, where Mohammed Sidique Khan exploded his; and at King's Cross and Russell Square stations, between which Jermaine Lindsay blew up his device.
A national two-minute silence forms the centrepiece of the commemorations at midday, signalled by the ringing of the famous Lutine Bell at insurance underwriters Lloyd's of London.
Bereaved families and survivors have been invited to visit the sites in the afternoon and a private service at St Ethelburga's Church in the City of London financial district at 3:00 pm.
But it is the 30-minute memorial service in Regent's Park at 6:00 pm that is likely to be the most painful for those caught up in what is the worst terrorist attack on British soil.
More than 1,000 people are expected to attend, including Marie Fatayi-Williams, 51, from Nigeria, who lost her oil executive son Anthony in the bus blast.
Mrs Fatayi-Williams, who has expressed a desire to meet the mother of her son's killer and for them both to denounce terrorism together, is one of a number of relatives who will read poems at the ceremony.
Songs to be sung by the London Community Gospel Choir include Labi Siffre's anti-apartheid anthem "(Something Inside) So Strong" and Simon and Garfunkel's "Bridge Over Troubled Water" before the names of the victims are read aloud.
Families and survivors will then complete a floral tribute, 12 metres across designed in the shape of a flower with seven petals to symbolise the date of the bombings, placing yellow gerberas in the centre.
Security will be tight in London and extra police have been drafted in although Scotland Yard has said there is no specific intelligence of any threat.
British policy 'motivating terrorism'
Meanwhile, extracts of a secret briefing document to police published by The Guardian newspaper have revealed the war in Iraq has had a "huge impact" on motivating Muslims planning acts of violence in Britain.
The newspaper, which said it had seen the report to senior officers at London's Metropolitan Police, said that British policy over Iraq and the Israel-Palestinian conflict is used by terrorists to justify their actions.
The document echoes the conclusions of an official report published last November that British foreign policy, especially in the Middle East, was a "key contributory factor" in radicalising some British Muslims.
Shehzad Tanweer, one of the suicide bombers who attacked London exactly a year ago, also said in a video released this week that there would be no let-up in violence unless Britain pulled its troops out of Iraq and Afghanistan.
British Prime Minister Tony Blair has consistently refused to acknowledge a link between extremism and his government's foreign policy.