The memorial to the 52 victims of the 7 July London bombings has been defaced by vandals on the anniversary of the attack nine years ago today.
Police had cordoned off the installation this morning as contractors were called in to clean the 52 pillars, one for each of the people killed.
A memorial service is due to take place at the site in Hyde Park later today, and this week political party leaders have been paying tribute to the "indomitable" spirit of London that was shown in the face of what was then its worst attack for more than 15 years.
According to reports this morning from London Live, the messages sprayed in red and black onto the memorial included the words "Blair lied thousands died", "Four innocent Muslims" and "July 7 truth".
The graffiti appeared to have been pre-planned, with the same words replicated across every pillar.
Scotland Yard said police had launched an investigation into the vandalism, and anyone with information was urged to call 101.
A statement said: "Officers were called by a member of the public shortly before 3.30am this morning and informed of the graffiti, which is being treated as criminal damage.
"Inquiries continue led by officers from Westminster - there have been no arrests at this time."
A spokesperson for the Tim Parry Johnathan Ball Foundation for Peace, which is organising the memorial for families later today, praised officials for organising the clean-up of the graffiti so swiftly.
"Today is about the families and the survivors, we are disappointed that it happened, especially for them, but the Royal Parks and Transport for London came out in force and it was cleaned up within a couple of hours," she said.
"They made sure that it is as it should be for today."
The monument cost nearly £1 million and has 52 stainless steel columns, or stelae, 11.5ft (3.5m) tall. It was unveiled in 2009 at a memorial attended by the Prince of Wales, the then Prime Minister Gordon Brown and other political leaders.
Four bombs went off in the co-ordinated attack in 2005, which saw 770 injured in addition to those killed. Three of the bombs exploded at 8.50am on Underground trains outside Liverpool Street and Edgware Road stations, and on another travelling between King’s Cross and Russell Square. One hour later a double-decker bus was exploded in Tavistock Square.
To mark the anniversary today, a minute’s silence will be held at the Hyde Park memorial, victims will speak about their experiences and the names of the dead will be read out, the Standard reported.
Speaking about the graffiti incident, the Mayor said: "I am shocked and saddened by this incident. It is completely unacceptable and the Metropolitan police is already investigating.
"I am pleased that the graffiti has been removed so quickly and that today's commemoration ceremony can go ahead as planned.
"The focus today should be, and indeed will be, on honouring the 52 innocent people who died on 7/7, the survivors and all those affected by the terrible events of nine years ago."
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies