The concept of a "guest beer" doesn't really exist in Ireland. What need have we of tied houses when we have, basically, a tied market? However, the handful of pubs who do interesting beer will occasionally bring in temporary stock and promote it as a "guest". The Bull & Castle Beerhall is doing so right now with Watou Wit, on draught for a limited period. This is a simple beer made incredibly well. It's pale blond and lacks the spice and fruit bells-and-whistles of many competitors. The result is an undemanding easy-going session beer: not too dry, not too fizzy but quality to the core. Especially recommended if you're a slave to the Hoegaarden or Erdinger taps.