both places were busy ,they are also right next door to each other.
both places were on the festival programme.
both places were busier because of the festival,my approach would be [if I had been drinking alcohol],to have an overpriced soda water[it was twice the price of the Lancaster]in the sub aqua club,then have a pint afterwards in the Leeds arms.
I think the sub aqua club would have been much quieter, trade wise without the festival,so while I can see their point of view over that, there is another way of looking at it :that sort of attitude by publicans,is of the variety of cutting off the nose to spite the face,[imo] if everyone did it it would be a problem,if only one person does it its hardly a problem.
of course another alternative would be for the sub aqua club to get a barrel of decent ale for the festival.
the main problem is the bringing the beer in to the pub,I am sure no one can object to anyone going in to the leeds,and having a pint,and then going next door to perform.but if the sub aqua club wants more trade,they are not going to get it by not allowing the festival,on the premises ,but they will get it by putting on a decent pint.
it is called being competitive.