Police investigating the theft of a phone belonging to Keir Starmer’s former chief of staff Morgan McSweeney have arrested a man.

The man, who was arrested on Wednesday in Peckham, south London, is suspected of receiving the phone after it was stolen, the Metropolitan police said on Thursday.

The government-issued iPhone, which was stolen shortly before 22.30pm on 20 October last year, has not been recovered.

Concerns have been raised that the theft could result in important messages about Peter Mandelson’s appointment as ambassador to the US being lost.

The whereabouts of McSweeney’s messages with Mandelson has been under intense scrutiny since it was reported that the work device was stolen shortly after Mandelson was sacked as US ambassador.

It was revealed in March that McSweeney did not disclose that he was Starmer’s chief of staff when he reported the theft of his phone. The Met released a transcript of the call, a highly unorthodox move, saying it wanted to correct misreporting of the incident.

The Guardian understands that not all of McSweeney’s correspondence has been lost and that the Cabinet Office holds a number of text and email exchanges between him and Mandelson.

A Met spokesperson said on Thursday: “Officers investigating the theft of a mobile phone in Belgrave Road, Pimlico, on 20 October 2025 have arrested a 28-year-old man on suspicion of handling stolen goods.

“The arrest took place on Wednesday 29 April at an address in Peckham. The man was taken into police custody and later bailed. He is suspected of receiving the phone after it was stolen and then selling it on. He is not suspected of any involvement in the original theft. The phone has not been recovered.”

McSweeney, who left the No 10 role in February, told police when he reported the theft minutes after it happened that it was a government phone. He said the iPhone had a tracker on it, according to the transcript of the emergency call. But he did not explain the sensitivity of the phone’s contents, records of the call suggest.