Many lessons were learned on Thursday:
Always take the right spare inner tube on a long ride. In this case NOT the mtb tubes.
Running home in bike shoes will hurt your toenails (but would have hurt them more if the inner tube had bust at Princetown instead of Holne)
During a roadside inner-tube change, discarded bic cases make useful extra tyre levers
That ring on the inside has a purpose in life just like the other two. In fact there is a whole world of gears down there once you accept that engaging them is not an admission of failure but actually…
… the route to happy going-up-hills-sitting-down, which saves the running muscles for the running bits – and is not noticeably less efficient.
On a road bike, there is no need to keep the thighs rigid and bottom hovering over the seat on downhill sections. Relaxing on the bike actually improves your speed.
In all a disastrous session turned out OK: 2 hr bike, 1 hr run, which if I hadn’t been intending a long bike ride I could have called a ‘brick’ session instead 
