A fifth man has been arrested in relation to arson attacks on properties and a car linked to Sir Keir Starmer last year.
The 19-year-old has been released under investigation after being taken to an Essex police station on Wednesday for questioning, the Metropolitan Police said.
The man, of Harlow, Essex, was arrested on suspicion of conspiracy to commit arson, police added.
It comes after a Toyota RAV4, which Sir Keir had previously sold, was set alight in Kentish Town, north London on 8 May 2025.
There was another blaze at the front door of a house converted into flats in Islington, also linked to the prime minister, on 11 May. Then, in the early hours of 12 May, there was a fire at the house where Sir Keir lived before he became prime minister and moved into Downing Street.
As part of the same investigation, three other men have been charged over the fires: Ukrainians Petro Pochynok, 34, and Roman Lavrynovych, 21, and Ukrainian-born Romanian national Stanislav Carpiuc, 26.
Lavrynovych is charged with three counts of arson with intent to endanger life, while Pochynok and Carpiuc are accused of conspiring to commit arson with intent to endanger life.
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Lavrynovych and Pochynok both previously pleaded not guilty at a hearing in October.
Carpiuc pleaded not guilty to the same charge in November, a court spokesman said.
They are due to stand trial at the Old Bailey on 27 April.
A fourth man has been released without charge, a force spokesman said.
