It's a gem of a place, serving a range of ales in a pleasant little pub, and often on the pavement outside. It's also a rather social little pub, where it's easier than most places to strike up a conversation with the happy customers.
Named after the Priory of St John of Jerusalem, founded in 1140, the current Tavern building dates from 1720. Your author agrees with the website blurb that it is one of the finest pubs in London and is pleased to report that it was voted 2009 Town Pub of the Year by the Good Pub Guide.
For more information, and even a podcast, visit http://www.stpetersbrewery.co.uk/london/default.htm