Exclusive: Boris Johnson in fresh inquiry after Jennifer Arcuri agrees to assist ethics watchdog

The American businesswoman, and the prime minister's ex-lover, is to let officials at London City Hall see extracts from her diaries

A fresh inquiry has opened into Boris Johnson's relationship with Jennifer Arcuri after the US businesswoman dramatically agreed to assist officials, paving the way for the prime minister to face possible criminal investigation.

Arcuri has formally offered to help the Greater London Authority (GLA) ethics watchdog by allowing it to inspect extracts of her diary entries chronicling her affair with Johnson and agreeing to be questioned for the first time by investigators over the relationship.