Hello Jo.
When we first encountered your son we was moored at the Anchor at Pyrford,when they came past us things were flying off our worktops, doors were banging,and the porta poti fell over,i shouted at them to slow down,but the noise from their radio drowned me out,there must have been at least 20 on board.
On their way back we were moored at Guildford,we heard them coming,they must have fitted the 2 new speakers,but we were ready for them,i had moored with 2 ropes facing out and 2 facing in,also 2 at a 45 degree angle from the centre hook,all to no avail,the wash they were making came over my tug deck and flooded the boat,there must have been at least 40 on board.
Apart from that they were no problem.