Mayor of London Sadiq Khan has pledged to do "everything possible" to prevent a tragedy like the July 7 attacks happening again.
It is 11 years since 52 people died and hundreds were injured in attacks on the capital's transport system in the single worst terrorist atrocity on British soil.
Khan said: "Eleven years ago our city came under attack, killing 52 people and injuring over 700 in four coordinated suicide bomb attacks across our transport network.
"Today, we remember those we lost and the heroic efforts of our emergency services and transport colleagues on that darkest of days.
"As Mayor, my first priority is to do everything possible to prevent a tragedy like this from happening again.
"By strengthening the bonds between Londoners from different backgrounds and focusing on real neighbourhood policing, we are making it easier for people to speak out and help root out and prevent radicalisation and extremism.
"We must also ensure that every single individual, and every single agency, involved in protecting our city has the resources and expertise they need to respond to any future major incident, which is why I have instigated a comprehensive preparedness review due to report later this year."
Britain's most senior police officer Sir Bernard Hogan-Howe will join the chiefs of London's fire and ambulance services at a wreath-laying ceremony in Hyde Park on Thursday.
Suicide bombers Mohammed Sidique Khan, 30, Shehzad Tanweer, 22, Hasib Hussain, 18, and Jermaine Lindsay, 19, brought horror to London on July 7 2005.
Travelling from Luton, they took a train to King's Cross in London, hugged and separated to carry out the atrocities.
Within three minutes of 8.50am, Tanweer detonated his bomb at Aldgate, Khan set his device off at Edgware Road and Lindsay blew himself up between King's Cross and Russell Square. Hussain detonated his device on a bus at Tavistock Square at 9.47am.