Dungeon Lane is a dump, merely a dreary track.    I’ve passed over it many times, always at about 20 metres – it runs alongside the southern boundary fence of John Lennon airport over which planes land. It goes nowhere, except to the airport viewing area #2.  Beyond that, just some scrubland and a boggy shoreline.  That’s all.    And yet, no doubt, it will be pulling in the crowds from all over the world, just like Penny Lane.    Paul McCartney is about to release his 18th so