Target one: get to the start. Achieved.
Target two: get to Hampton Court in time to make our own decision: Achieved.
We had a serious conversation about timing - having arrived at Hampton Court pushing quite hard at about 10:45 (110 minutes to do 27 miles is decent going into a headwind) we had 7 hours to do 60-odd miles (Leith and Box having been abandoned some weeks ago). That sounded achievable.
Then
@rvw pointed out that when I wasn't concentrating I was completely vacant and we'd probably have more fun enjoying a shorter ride on closed roads than trying to chase a cutoff time. So we turned for home adn 46 miles, and, do you know what? She was right. We had a reasonably gentle potter from Hampton Court to the end, stopping several times to inhale water and power bars and letting the field pass us. The support we, and all the riders got, in that section, was very welcome. Being an odd bike we got more directed vocal support than most. I believe we did see
@mjr twice (each time counting double, as it were) - on the exit from the Limehouse tunnel and on Putney Bridge. On the other hand I was slightly confused - he apparently had a Dahon on Putney Bridge whereas I'm sure I'd seen him much earlier on a Brompton on the Bow Road as were groping our way towards the start line.
I can't (obviously) speak for the set-piece hills, but both the rise out of Kingston town centre and the hill out of Wimbledon did for some people. We even managed to overtake a soloist in Wimbledon. He was stomping very hard and very slowly at the bottom of his sexy racing double. We were winching ourselves gently up in the lowest 28 x 30 gear of our immensely practical, if not sexy, touring triple.
In general I thought the riding was pretty decent, even if one person was a little optimistic in trying to squeeze through our inside as we went to the left on one of the rises on the Hammersmith flyover. He got an earful and was, I think, chastened. On the other hand some of the pedestrians were dozy. I don't ever particularly ever again want to shout "Stop, Stop" at a crocodile of several dozen schoolchildren (at a guess, first language not English) while hauling on the brakes knowing that we were all at risk of being run over by several hundred cyclists chock full of adrenaline and only just warmed up. (That happened on the first run-in to Trafalgar Square). And, very sadly, we passed the aftermath of an incident in Chelsea where an elderly local woman walking her dog had apparently been knocked over by a cyclist who, not unreasonably, expected the closed road to be closed - even to locals and their dogs.
Apparently the back half of the tandem managed to cross the line after 46 miles in 3:36:39, a full 20 seconds before the front half (3:37:06), who (even more oddly) had no timing chips in his name. But we weren't after a time.