UBSS talks may well be free but this isn't a UBSS talk, its a Wilderness lecture that just so happens to be held at Bristol University. Wilderness lectures have been running since 1987 and as far as I know you have always had to pay.
Gina's N. E. Greenland lecture will be an excellent event that shouldn't be missed. Robbie Shone's photographs of the expedition are a must see for anyone interested in the area. Whilst the expedition certainly didn't find the longest or deepest caves in the world, the 20+ caves the expedition did find are the most northerly explored caves in the world.
Mark