London's abandoned rail and tube lines have been put to many novel uses down the years functioning as bomb shelters, impromptu party venues and film sets for Hollywood movies.

But a new idea to create a mushroom garden in a tunnel beneath Oxford Street is perhaps one of the more unconventional attempts to breathe new life into the UK capital's forgotten subterranean murk.

"Pop Down" imagines a section of the defunct "Mail Rail" tunnel - a narrow gauge railway used for transporting mail around London which closed in 2003 - being repurposed as a mushroom farm and pedestrian walkway lit at street level by glass-fiber, mushroom-shaped sculptures.

Read the full story: "Mushroom garden" offers tunnel vision for a greener London