On flat, a gnat’s under 25 mins. And I mean dead flat, it was an outdoor track.
28 mins is not bad if you had traffic problems.
If you want to test yourself properly you need a route without traffic lights or busy junctions, and that’s out and back. Dual carriageways are good for this – start five miles from a roundabout and you can turn round without having to slow much. Grim riding tho, but that’s the whole point 🙂 Sometimes industrial estates have suitable drags that are quiet after working hours.
If you can get to Reading there’s an outdoor track there you can use.
EDIT: lol@tags 🙂