Where to find the best Guinness in London

London has always been dogged by the canard that the Guinness here can’t compete with what’s served across the Irish Sea. It is certainly difficult – perhaps impossible – to replicate the quality of the pints in Mulligan’s on Dublin’s Poolbeg Street, or at the Gravediggers by Glasnevin Cemetery. However, there are pubs here that do it admirably – if you know where to look.