Don't know if you have visited this area before but from Peterborough to Kings Lynn isn't very interesting being pretty flat and boring. The roads can be pretty dangerous as well being long and flat. A road that is slightly off your route but in the middle of nowhere has had average speed cameras put on it as the local council did a survery after several cars left the road and ended up in the adjacent deep dyke canal. The occupants all died. The fastest car they recorded was 148mph

and
average speed was 88mph

. This is on a 50mph speed limit road (B1049). Anyway I think it is slightly off your route, plus it now has average speed cameras on it

.
From Peterborough to Kings Lynn try and avoid the big roads at all costs especially the A47 as the traffic can be heavy with lots of heavy lorries and fast moving traffic. There are lots of accidents on the A47 especially at Guyhirn, junction with the A141.
From Kings Lynn up to Hunstanton the flora becomes a bit more interesting as it is microclimate I think. You see a few more exotic trees and shrubs. The A149 from Kings Lynn up past Sandringham (call in to say hi to Liz and Phil

) to Hunstanton can also be very busy and not a pleasant place to cycle as it is single carriageway. Maybe you could take the B road through Dersingham and Snettisham or just miss out Hunstanton and go straight for Brancaster following the B1153 inland through Docking which is quieter. Beware caravans as well, loads of them in summer

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The scenic bit really starts from Brancaster just round the coast from Hunstanton (Brancaster beach is very long and wide depending on tide, nice golden sand as well), Wells very pretty (Holkham Hall nearby), there is a nice campsite on the beach with nature reserves all around at Stiffkey just past Wells. A bit basic but nice none the less. Blakeney (Seal boat trips to Blakeney Point, a very pretty harbour and town), Cley-next-the-Sea again small and very pretty (Cley windmill has a cafe in the base which serves excellent tea, scones the size of dinner plates and cakes - home made and huge portions (May '08). Road through Cley is very narrow), are all very pretty. There are lots of bird reserves and walks along this part of the coast so lots of twitchers and hides in the dunes. There are quite a few camp sites, tea shops, tat and arty shops in the smaller places as well. The roads can be very narrow in places and the traffic heavy in peak times and on fine week ends. The route is pretty flat becoming slightly undulating inland. After that toward Sheringham and Cromer the scenery tails off a bit. At Cley after tea and scones you could cut south to Holt, very picturesque, down the B1149 to Norwich rather than the busy A140

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Cycling Weekly last week page 55 had a Norfolk training route part of which was Brancaster to Cley to Holt. The guy Duncan Urquhart lives in Watton near Swaffham and rides it regularly as it is a quieter route. I've also ridden it a few times myself

and also been in the car a few more times

. IMHO it is certainly a nice ride well worth doing. Just that the traffic can be heavy on a nice weekend and olidays.
Good luck.
