After much cajoling and bribery. Actually, just us sticking at encouraging him. In two weeks, Daniel has gone from falling off his bike every few metres and giving up, to cycling unaided for 5 miles in one go. He is now unstoppable, and him Hannah (and Zoe) are always asking about getting out on their bikes. Daniel has already progressed to the bigger bike.
This is great for us, as now we can all get out. I ran (jogged) alongside Daniel for 4 miles on Tuesday and struggled to keep up. So this will either kill me or help me get fitter.