Me and a bunch of friends have been doing this for a decade. Use it as an excuse to meet up annually.
Choose a spot in London we don’t know very well and visit 12 pubs near there. Usually find you get a few gastro pubs, some old school boozers and a handful of REALLY shady ones. Got to see some lovely spots over the years such as Willesden, Rotherhithe, West Brompton, Tottenham Hale, Leyton and Deptford.