James Boyle abused the girl, who was under 16, between 1986 and 1991 while serving for Cambridgeshire police.

The 69-year-old, of Sunbury Street, Edinburgh, was convicted by a trial jury of two counts of rape and one count of indecent assault.

Detectives said they were told about the offences in 2018 after an "exchange of messages on social media".

Detectives said Boyle was still working as a criminal defence barrister at the time of his arrest

"I want to praise the bravery demonstrated by the victim in this case for coming forward," said Det Sgt Carla Hillyer, of Essex Police, who said Boyle was still working as a lawyer at the time of his arrest.

"Boyle worked as a criminal defence barrister, he knew this system, and what the victim was up against."

Essex Police said the offences happened at different locations in Cambridgeshire.

'Tirelessly'

Constabularies from elsewhere in the UK routinely investigate cases where the relevant police force is deemed to have a potential conflict of interest.

Ms Hillyer also commended the work of her colleague Det Con Adam Clarke who she said "worked tirelessly" on the case.

Boyle is due back at Cambridge Crown Court for sentencing on 25 May.

Essex Police said there was advice and guidance for "anyone affected by rape and sexual abuse" via the Synergy Essex website, which is a collection of support organisations independent of the force.