to answer Wil's point. Bletchley is not difficult to reach from Cambridge by car, it just isn't on the doorstep. Again not especially difficult by train, just time consuming.
By car I'd use the A428 dual carriageway to St Neots (becomes single carriageway approaching St Neots), then a very short stretch on the dual carriageway A1 (50 mph speed averaging cameras in stretches) to the dual carriageway limited access A421 towards Milton Keynes, then follow the sat nav around the roundabouts and follow signs towards Bletchley and then the Station and it is nearly across the street. A little over an hour if the traffic doesn't get you.
By train, fast train from Cambridge 48 minutes to Kings Cross Station in London, 10 minute walk or 3 stops on a bus or 1 stop on the Tube to Euston station, about 35 minutes by train to Bletchley, out the door, turn right, cross the road, you're there.