Devon Tory election expenses conflict?

From a correspondent:

West Mercia’s Assistant Chief Constable (ACC) Chris Singer was with Devon and Cornwall police until Dec. 2015, the Commander for Plymouth and before that Torbay.

Even if no Election Expenses offence was committed by Alison Hernandez and Kevin Foster, any outcome may be tainted by Devon and Cornwall Police passing that to a force whose ACC was with them at the time of the General Election in May 2015.

Does any potential conflict of interest in passing that investigation to West Mercia risk bringing both constabularies into disrepute?

Indeed, a very good question.