Cambridge, like York, is not a city built for cars, which won't help your situation. I don't know your background, if you'll have a blue badge, but whatever you end up doing, research your parking and route to the car park carefully or you'll end up having an immensely frustrating experience!

(Also, do note that there's long-term roadworks on the section of the A14 between the A1(M) and the M11, which can cause quite severe delays at peak times. Not necessarily a problem, but do watch out.)

Now the negatives are out the way... Cambridge is a wonderful place - I'm very lucky to have it as my nearest city. The obvious attraction here is the colleges, like you'll have seen in Oxford, but the stretch of the Cam along the "backs" (the backs of the colleges along King's Parade and St John's Street) is quite unique. The best way to see it is from the river, and Scudamore's do punting excursions. Note that the Cam is in several sections separated by locks and weirs, so for the backs, you'd need to pick up a punt at Mill Lane.

There's a lot of museums in the city, from the eclectic Kettle's Yard, to the Fitzwilliam Museum, to obscure academic ones (the museum of zoology has a fine selection of pickled things in jars). The Orchard at Grantchester's an excellent suggestion, too.

If it sounds like too much hassle for this particular trip, there are other stop-off points you may consider. Stamford (in Lincs) just off the A1, is an incredibly well preserved old market town, built out of the lovely local stone, where you can eat in the George Hotel, a pub dating back over 1000 years. Burleigh House is the main attraction in the town, although a walk round the town centre itself is pleasant enough.

If you choose to carry on down the A1 instead of the M11, you go past my neck of the woods. Old Warden, just off the A1, is an odd little village, modelled in the style of a Swiss village, in the Bedfordshire countryside. The Hare & Hounds pub has great food (as does the Black Horse, in the village of Ireland, slightly further on). Just outside the village is Shuttleworth, an eclectic vintage aircraft and car collection, together with a Swiss Garden (and agricultural college). You can also get a good pub lunch in Willian (the Fox). Slightly closer to London (perhaps too close) is Ayot St Lawrence, home to Shaw's Corner, the preserved home of George Bernard Shaw (with the lovely Brocket Arms next door) which is rather pleasant.