I had problems with groups a few times; they'd chase me down, assimilate me into the group, then slow down (presumably because they'd burnt themselves out chasing me). So my cruising speed, which had been say 28km/h, would drop to 24km/h. And because I'd be on the the right in the middle of their group, I'd have to fight my way out to accelerate back up - at which point the group would drop behind.
This happened three or four times, with different groups. Not a big issue, just irritating - like those who'd do similar then descend like grannies, blocking me in and forcing me to be on the brakes all the way down.
But things I learnt -
Despite what AndyH claims, Pain Au Raisin doesn't exist
I really do prefer having tribars for long rides.
It is expensive leaving your family in Paris whilst you go off on a bike ride.