Scotland Yard asked for legal advice from the attorney-general about providing a taxpayer-funded blue-light escort for Taylor Swift over concerns that officers could be held liable if there were any accidents.

Lord Hermer, the government’s top lawyer, was asked to intervene after Scotland Yard warned that granting the US pop star “VVIP” protection would breach its longstanding protocols.

The Metropolitan Police are said to have felt pressured after Yvette Cooper, the home secretary, and Sadiq Khan, the mayor of London, held talks on providing protection for Swift during two of her Eras Tour concerts at Wembley in August. Sue Gray, then the prime minister’s chief of staff, was also involved in the discussions. The government and Khan have insisted that the decision was left to police chiefs.

The police argued during the talks that there was no justification for providing Swift with the protection because there was no specific threat against her. The service, provided by the Met’s Special Escort group of motorcyclists, is usually available only to members of the royal family and senior cabinet ministers.

Scotland Yard eventually relented after asking Hermer for legal advice in response to concerns that officers could be culpable if bystanders were injured or killed while Swift was being escorted.

“There were questions over the legality because the police were being asked to exercise their powers against usual protocol,” a source said.

Addressing the row on Monday night after a speech at Gray’s Inn in London, Hermer told his audience: “There is a convention that forms part of the ministerial code that prohibits me from saying whether I have advised ministers — and certainly prohibits me from saying what advice I might have given.”

The issue is a sensitive one for Scotland Yard. In May last year an 81-yearold woman was killed in a collision with a motorcycle that was part of an escort for the Duchess of Edinburgh. Christopher Harrison, a 67-year-old police officer, was charged this month with causing death by dangerous driving.

Swift’s mother, Andrea, held talks directly with senior officers and is said to have threatened to cancel the singer’s shows after her concerts in Vienna were abandoned in response to a suicide-bomb plot that was foiled by the CIA. Days earlier, Axel Rudakubana, 17, had been charged with murder over the mass stabbing at a Taylor Swift-themed yoga and dance class in Southport.

Swift’s mother is said to have pushed at first for an armed police escort, a request that was rejected outright as protocol states that it is usually reserved for the heads of foreign states.

Scotland Yard eventually agreed to provide the blue-light escort.

Both Khan and Cooper received free tickets to Swift’s concerts, on August 15 and 16 respectively, which were declared properly.

The government has insisted that operational decisions were made by the Met and denied suggestions that the discussions were linked to ministers attending the concerts.