One of Boris Johnson’s closest aides, Lord Udny-Lister, is leaving his role as the prime minister’s special envoy to the Gulf, Downing Street has said.

The 71-year-old peer, who served as Mr Johnson’s chief of staff when he was mayor of London, had been appointed to the post earlier this year.

He was first brought into No 10 as chief strategy adviser when Mr Johnson became prime minister in 2019.

No 10 said Lord Udny-Lister had “been an outstanding servant to the country”.

A Downing Street spokesman said the prime minister “is hugely grateful for Lord Lister’s dedicated service over many years… to the government and to the prime minister when he was mayor of London”.

Earlier this month it was confirmed that Mr Johnson had asked Lord Udny-Lister, a Middle East expert, to check on a Saudi Arabia-backed takeover bid of Newcastle United Football Club.

It came after the Daily Mail reported the prime minister was contacted when the £300m deal ran into difficulties.

The government denied it was involved “at any point” with the failed bid.

Downing Street said Lord Udny-Lister was asked to look into the progress of the deal but was not asked to intervene.