A retired police officer has offered £100 from his pension as a reward for information to help catch the vandal who splashed white paint on PC Yvonne Fletcher’s memorial.
John Murray was with PC Fletcher when she was killed in April 1984 as shots were fired from the Libyan Embassy in London at a protest outside.
Her memorial in St James’s Square was among five vandalised last week.
No one has been brought to justice for her murder or the vandalism.
Mr Murray, from Chingford, north-east London, said he was putting up the money for any information leading to the arrest and conviction of those responsible for the “heinous act” of vandalism.
“It’s disgraceful – when I saw the photograph I was just gutted,” he said.
“I go there once a year to lay flowers and I have done for the last 34 years.
“Because I was standing next to her that day and we changed places three or four times I think if we had done it once more it could have been me.
“I regard [the memorial] as almost a personal shrine. I made a promise to find out what had happened and every time I go there I repeat those words.”
The Met is trying to trace the vandal, who is believed to have worn ski goggles and a face mask as he splashed white paint on the memorials.
As well as the Yvonne Fletcher Memorial the vandal targeted the Allies Statue of World War Two Prime Minister Sir Winston Churchill and US President Franklin D Roosevelt in New Bond Street.
Police believe the suspect first struck at the Bomber Command Memorial before heading along the Mall towards Trafalgar Square, passing Canada House in the direction of St James’s Square, before ending on Jermyn Street.