Grand Union Canal, MK to Tring

We cycled south down the Grand Union canal from Loughton in MK, across Bletchley and joined the canal, then headed south towards the Three Locks.  It was a fast average speed of 12 mph and good progress.  Along the way a dog chased us but we were too fast.  Also a woman got stranded in the canal and we had to pull her longboat to the side of the canal - good deed of day #1.  Nice and smooth hard surface all of the way to the mythical city of Leighton Buzzard.  We stopped for tea and pushed on south past the LB bypass.  At this point the canal towpath turned to a rough track and slowed us down to 9 mph. At Horton a woman was stuck trying to open one of the locks so we pushed open the lock gates for her (good deed #2).  Just north of Marsworth I got a puncture and we needed to fix that as the tyre was completely and totally flat.  This cost us a bit of time.  At Marsworth it started to get dark, and we speeded up.  Then we came of the canal at Tring station and had to wait 50 minutes for a train back to Milton Keynes station.  Every train seemed to zoom past Tring without stopping, but our train was quite fast and it only took 20 miniutes to get back to MK with one stop at Bletchley.  Total journey of over 24 miles. Easy.  Next time MK to Watford.