My usual route (I've done it 20 times or so):-
http://www.bikely.com/maps/bike-path/71351
Up the A10, continue straight onto the A1010 at Bruce Grove. There's no real nice way of getting out of London, the A10 and A1010 are fine to cycle along and get the job done quickly.
If it's early enough in the morning then you can cut through the shopping area at Waltham Cross, otherwise go round to the right and then left at the next roundabout to avoid it. Continue north onto the B176 at the roundabout, last exit, signposted Turnford or Wormley.
Straight on on the B176 all the way to the edge of Hoddesdon, at the big roundabout after the Sainsbury's where the main road goes left you go right (Essex Road Industrial Estate) but, within 30 yards, nip up onto the pavement and across the bit of pathway and right onto Stortford Road.
(Look at the above bit on the map to see what I mean.)
Left at the end of that road through some bollards and then right onto Rye Road. Over the couple of bridges (railway and river/canal) and down towards the Nature Reserve over the speed bumps. Through the barriers across the road at the water works (don't worry, it's all ok to do this) and up the hill. Left at the top, over the A414 and first right (Kitten Lane) just as you start to drop down the hill (easy to miss). Right at the T-junction at the end of Kitten Lane (not very good visibility) and you're on the B180.
Continue north on this road for ages. At Widford you'll come to a T-junction where you want to continue North (right) on the B1004. Through Much Hadham and straight on (North) where the B1004 turns off to the right towards Bishop's Stortford.
Through the other Hadhams and Right, imm Left and the A120 crossroads (traffic lights may take ages).
Straight on (keeping right at the fork for Furneaux Pelham) and turn left at the remains of the burnt down pub in Stocking Pelham (they may have rebuilt it by now, or razed it to the ground).
You'll then come to a grass triangle at the B1038, left here and up the hill where there's often a git of a headwind too.
Straight on in Brent Pelham (B1038 turns off to the left). Right at the next grass triangle in the road towards Langley. Left at T junction then right at The Bull pub and up towards Langley.
Left at the village green (by the bus shelter). Marvel at the cricket square on your left and the fact that the cricket pitch extends over the road you're on. Up out of Langley and the S bends to the right then left.
Through Duddenhoe End and Pond St following the road straight (i.e. without turning off). Left at the T-junction onto the lovely surfaced B1039. First right in 2km or so and climb up into Chrishall. Right at T in village by grass triangle in road and continue North.
Keep going North as it flattens out and right hand turn (unsignposted) called Grange Road. It's the right turn about 500m after the left hand turn that is signposted Cambridge (oddly). This takes you round the back of Duxford Imperial War Museum and over the M11 into Duxford village. Straight on at cross roads at the end of this road and follow the road round to the left.
Cross the big nasty A505 by using the pedestrian island in the middle, there are some blue cyclepath signs that'll show the way. It's reasonably obvious what to do. Continue going North.
Once straight over the A505 go up the little climb (on the path) and rejoin the road. Past the turning for the station and through Wittlesford to Shelford. Follow the road straight on, there's a sharp right turn in the road just as you come into Shelford, follow it to the right.
Past the church in Shelford and keep to the left where the road forks. Up to the junction with the A1301 with a Lloyds bank on your left. Left at this junction onto the A1301 and shortly turn right onto Granham's Road at the bottom of the humpbacked bridge.
Over the level crossing and, straight away, left onto the path. There's a useful cycle path along the side of the railway and through the fields to the back of Addenbrookes. Much nicer than either road option.
Follow this cycle path all the way to Addenbrookes and turn right onto the hospital ring road. Follow the ring road round to the main roundabout at the entrance, right (3rd exit) there, then left (first exit) at the big roundabout on Hills Road. Straight on at the traffic lights at the Hills Road/Long Road junction. Keep going that way and you'll be in centre ville.
