Beginning of the financial year, mileage allowance 45p/mile. He can't have already clocked up 10,00 miles in 28 days to be getting the reduced rate of 25p/mile - can he? 90p gives him a two mile journey for each log entry. Maybe he just popped out for lunch: Hare & Hound, up Pimlico way, Star & Garter, south bank, Fiddler's Elbow, Camden Town, The Granny Knot, Bayswater, The Frog & Whistle, Lambeth - the list is endless depending on direction from place of work.
Mind you, I'm assuming he was alone in the car because otherwise he'd be entitled to an extra 5p per mile for every "qualifying" passenger and that makes the maths too difficult (wish I'd paid more attention to Miss Wilkinson)!