IMHO the Norwich Castle is a must see for anyone going to England. The dungeon is enough to give you the willies even today. There are also great walks around town and the Cathedral is not far. Fly into London but get out to the cities and villages as soon as possible. I still have friends who live outside the town and deal in small antiques and what we would call nick nacks. They used to get some of their stuff from the old “tips” (dumps) from Norwich. Great stuff that was just thrown away back then.
My wife grew up in Norwich, and we visited the city last year. A very nice place. She has a sister who lives in Easton, and we took the bus into Norwich several times. Interesting to see all the old, and I mean real old, buildings including the old Roman wall still standing. In the States old means only about one hundred years or so. In Britain it’s around five hundred to two thousand years. or longer if you count Stonehenge we we visited also.