SADIQ Khan and Met chief Cressida Dick honoured the victims of the 7/7 bombings on the 15th anniversary of the London attack this morning.
The attacks on three London Underground trains and a double-decker bus killed 52 people and injured more than 700.
The London Mayor and Metropolitan Police chief laid wreaths at the memorial in Hyde Park to pay their respects.
They paid tribute at 8.50am – the time the first bomb went off.
A message on the wreath laid by Mr Khan said: “Fifteen years have passed, but the 52 innocent people who lost their lives on 7/7 remain in our hearts.
“Those who seek to divide our communities and destroy our way of life will never, ever succeed.”
The group this morning also included British Transport Police Chief Constable Paul Crowther, City of London Police Commissioner Ian Dyson and Transport for London Commissioner Mike Brown.
A second group, including London Fire Brigade Commissioner Andy Roe and London Ambulance Service chief executive Garrett Emmerson, laid wreaths at 9.47am – the time the bomb on the bus detonated in Tavistock Square.
A separate virtual service for families of the 52 people and survivors will being held in the afternoon.
Marking the anniversary, Mr Khan said: “Today we honour the 52 people who lost their lives and more than 700 who were injured on July 7, 2005.
“Our capital will never forget the terrible events of that day, and my thoughts are with all those whose lives were changed forever.
“As we mark 15 years since the attack on our city, I want again to pay tribute to the heroic efforts of our emergency services and transport workers, who ran towards danger to save lives, on that awful day.
“The way that our city responded and stood united in the aftermath of the attack showed the world that our values of decency, tolerance and mutual respect will always overcome the hate of the terrorists.
“Today, we reaffirm our commitment to upholding these values. To those who wish to divide us and spread hatred, we send a clear message that they will never succeed, and that we are stronger together.”
Comissioner Dick remembered the 52 who were “so cruelly snatched away” 15 years ago.
She added: “We think also of the way our great city of London reacted. Those we lost represented the best of our city – diverse, strong, wonderful people.
“As a city, London was not bowed, we came together, we supported each other and we have continued to fight the scourge of terrorism ever since.
“Today, I think also of my officers and staff who ran towards those terrible scenes. Who put themselves in danger and tried to do their best to support those affected.
“On behalf of everybody in the Metropolitan Police Service, we will not forget.”
London’s Transport Commissioner Mike Brown also paid tribute to the tragic event.
He said: “We will never forget those innocent victims who lost their lives in the most tragic circumstances 15 years ago.
“We stand united with our colleagues from the emergency services and the city as a whole in remembering them today.
“The resilience of great world cities like ours continues to be tested but Londoners have shown time and time again that our strength lies in our diversity, resourcefulness and spirit of togetherness.”
On July 7, 2005, four suicide bombers detonated explosives during the morning rush hour on Tube trains at Edgware Road, Aldgate and Russell Square.
A bomb was also detonated on a bus at Tavistock Square.
The attack left 52 people dead and more than 700 injured.