Riding my first audax in April (200k down and up the Vale of York), our route coincided with a local sunday morning TT.
Although I was tempted to try and chase down the lad who overtook us with his disc wheels and pointy hat, it wasn't a problem, until we were approaching a crossroads at the top of the hill, and I shouted "Straight on" to the lad I was riding with. As it happened, this was the point where someone on the TT had caught up with us, and being a bit addled from his efforts up the hill, he paid attention to me and started to go straight over the crossroads, until the helpers shouted frantically that he needed to turn left, and I held back to let him turn left across me.
It's a pity - we nearly had him join our ride, and I wouldn't have minded following his wheel for 180k