Mr-T

The reason he just 'let you off' is probably because he didn't have, or couldn't get, documented evidence of the speed you were doing using the onboard camera or whatever.

If he had been able to get some he would have shown you it before you parted company.

Without this it would have been pointless him issuing a ticket as if you'd decided to contest the issue and it had got to court there would have been no proof for them to present.

Result for you though!