A man has been arrested on suspicion of urinating on the Westminster memorial dedicated to hero PC Keith Palmer.
The incident is believed to have taken place on Saturday afternoon during demonstrations by far-right protestors.
Mr Palmer, 48, was stabbed while on duty during the Westminster terror attack on 22 March 2017. He was one of five people murdered by Khalid Masood.
The image of the man was widely shared on social media throughout Saturday.
The Met Police said on Sunday morning that officers had arrested a man on suspicion of outraging public decency.
He is currently in custody in Essex after presenting himself at a police station.
Speaking on Saturday in response to a photo posted on social media, Commander Bas Javid said: "We are aware of a disgusting and abhorrent image circulating on social media of a man appearing to urinate on a memorial to PC Palmer.
"I feel for PC Palmer's family, friends and colleagues.
"We have immediately launched an investigation, and will gather all the evidence available to us and take appropriate action."
MP Tobias Ellwood, who gave first aid to PC Palmer as he lay dying after being stabbed in the grounds of Parliament, said the image of the urinating man was "abhorrent".