At about 11 o clock last night I heard the main door in our block of 4 flats open. I heard voices...looked through the spyhole and saw my neighbour opposite had opened her door and there was a uniformed policeman standing on the stairs...he didn't come all the way up to the landing.
He was talking to my neighbour and then he went.
Today she told me he had buzzed her door and said "Police" so she let him in...then on the stairs he asked for a woman who doesn't live here...said a name we've never heard.
She said there was nobody here of that name and he asked her "how long have you been here?" and she said "A year...can I help somehow?" and he said "No...it's just a job..." and then went. 
We had it transpired both looked out of the window as he left in a normal silver car.
She wondered why he came alone in an ordinary car and had no radio or backup....don't they usually have a 2nd officer in attendance?
Is it odd? Dodgy? Should she report it to the non emergency number? I noted that the man didn't walk very well..his breathing was laboured and he limped quite heavily. He didn't seem very like a normal policeman iykwim...like he wouldn't manage or something...