It's amazing what you can do for £20. You can ride a train that goes 200 km/h non-stop from London's King's Cross to Cambridge in 45 minutes, non-stop. Think: Chicago to Milwaukee in 45 minutes. Vroom.
Cambridge was certainly worth the trip. I didn't do the main touristy thing (punting down the Cam) but I did watch others do it:
Of course there's King's College, founded 50 years before Columbus reached America and 490 years before my alma mater:
Speaking of really impressively old, the place where I had lunch opened in 1525, and among other patrons counted Drs. Watson and Crick while they were, you know, discovering DNA and all:
Lunch? Bangers and mash with a pint of Old Speckled Hen real ale: