This is an event organised by The Chap magazine and takes place on 17th May.

The meeting point this year is changing to Covent Garden in the outdoor areas to Courtyard Wine Cellars which is a warren of converted cellars beneath Covent Garden Piazza at midday and the walk has no fixed route. People saunter through London in their finest dandy, flaneur or vintage outfits to observe the city and be observed. so expect Suits, top hats, walking canes and other dandyish attire.

This looks like it will be a good photographing opportunity.