Bit late on this but the Something Lovely tearooms in Puckeridge are a very good midway stop in a London - Cambridge.
In case the route was at all up for debate, I'd suggest getting out of London via Hertfordshire rather than the Lea valley. The latter is quicker but far uglier on long straight A and B roads with no great views and a fair bit of traffic. Even then, I'd avoid the B road kind of parallel to the A11 and keep to the small and slightly more meandering lanes to the east of it (via Cold Christmas, Barwick Ford, Anstey and up to Great Chishill with great views of the windmill) - some amazing lanes to be found there!
If leaving London from the east side following the route 1 and 11 from the Sustrans maps looks to potentially be a nice route too, as it follows many smaller lanes which tend to be very nice and rolling with some lovely views in that area.
Bit late on this but the Something Lovely tearooms in Puckeridge are a very good midway stop in a London - Cambridge.
In case the route was at all up for debate, I'd suggest getting out of London via Hertfordshire rather than the Lea valley. The latter is quicker but far uglier on long straight A and B roads with no great views and a fair bit of traffic. Even then, I'd avoid the B road kind of parallel to the A11 and keep to the small and slightly more meandering lanes to the east of it (via Cold Christmas, Barwick Ford, Anstey and up to Great Chishill with great views of the windmill) - some amazing lanes to be found there!
If leaving London from the east side following the route 1 and 11 from the Sustrans maps looks to potentially be a nice route too, as it follows many smaller lanes which tend to be very nice and rolling with some lovely views in that area.