I was charged last time I booked for the Trafalgar and had a battle with ATG to get my £3.50 back. Apparently there is now no way of avoiding a fee - not even if booking in person, I was told when I called in to ask. So I don't go there any more.
The trafalgar studios website says
All tickets purchased by phone or online at atgtickets.com incur a £3.50 per transaction fee. Per ticket booking fees may also be payable. There is no booking fee when booking in person at the box office.
So maybe this has changed?
Maybe, and it would be great if it had. Not only does it deter people from booking but it's another of those disproportionate fees which clobbers people (like me!) booking a single, cheapish ticket. A pain to have to go back to check though, and then perhaps to book: further reports welcome.