Ken Livingstone, the Mayor of London, laid lilies and Tessa Jowell, the Culture Secretary left white roses at the spot in the Victoria Embankment Gardens, near Embankment Underground Station, in a silent ceremony yesterday. Senior police officers and leaders of the city's Christian, Muslim, Hindu and Jewish communities also participated.
They signed a book of remembrance that will be left in a tented enclosure for members of the public to join the mourning. The tree under which it stands was planted by the Queen to mark her accession to the throne in 1953.
The London Memorial Garden was established by Westminster City Council. A second will be opened in Russell Square, near the site of one of the Tube bombings.
Mr Livingstone wrote: "The city will endure. It is the future of our world - tolerance and change." Ms Jowell wrote: "The strength of London and her people is in diversity and tolerance. Our deepest sympathy is with the grieving families."
Explaining the decision to establish the garden, Simon Milton, the leader of Westminster City Council, said: "This is a beautiful park for all Londoners and visitors to have their private thoughts and pay a silent tribute if they wish.
"We knew that tributes would spring up in all sorts of places. People have a right to lay their tributes where they want.
"We wanted there to be a place in a beautiful spot where people will have time to contemplate, not just outside a busy station, and to sign a book of condolence and have a space for peaceful, quiet contemplation."
Commander Frank Armstrong of the City of London Police, said: "I am sure it is hugely important and many people will come from diverse communities in London to sign the book just as I'm sure many many people will visit."
In other expressions of condolence yesterday, the Bishop of Stepney, the Right Rev Stephen Oliver, wrote: "With the prayers of all the faithful people that peace may be the life we share together."
The chief executive of the Board of Deputies of British Jews, Jon Benjamin, wrote: "With our heartfelt condolences, our thoughts and prayers for peace. Shalom."
Lord Coe, head of London's Olympic bid, wrote: "London can only gain strength - emerge stronger. Our thoughts are with so many."