interesting possible uncredited cameo, want others feedback.

When the police car delivers Mr Larkin (the critic who gets drowned int he vat of wine) to the 'wine tasting', the police officer driving the car is speaking into a micorophone, then gets out of the car and follows the critic for a few steps, asking him how long he expects to be. the voice is not the normal speaking voice of who it looks like, but does sound more than a little like another voice done by the man i could swear it is...

I could swear this walk on part is a cameo by Monty Python's Graham Chapman. He is not, however, credited. i know that he popped up in several films in minor roles in the sixties, and no reason he would not have done this one, but have been unable to find any corroboration.

Failing corroboration an anyone else at least confirm to me that it sounds like one of Chapman's voices and looks like him?