Mildmay Hospital became famous when Prince Diana became a regular visitor in the 1990's. In all she went there 17 times and would arrive in the evening to sit with patients, some who were dying. She had the knack of making people feel at ease and cared for. Prince Harry has followed in the footsteps of his mother, and recently met staff and patients during the official opening of the new £6m hospital. It's wonderful that this inspiring institution now has a London Overground line named after it.

Author Mark Ovenden, pictured right, is an unlikely underground railway fan. He's been a Producer for Radio 1, Kiss and the Ministry Of Sound and also run a satellite tv channel. OutUK's Mike Gray talked to Mark about why he created the book.

OutUK: Where did your interest in Metro systems begin?
Mark: Being brought up as a kid in London you get pretty used to the tube - then having it taken away just when you want to start going out and being independent makes you acutely aware of how important things like easy access to quick, safe, clean rapid transport can be. My parents moved us to the Isle of Wight when I was 13 and about to discover my sexuality. Suddenly that wonderful anonymity and bustle of a huge city like London with its excellent transportation was replaced by a pretty poor bus service on which everyone knew everyone else.

OutUK: Is it the design of the maps which attracts you?
Mike: The smell of them maybe? The fact they've been in the jean pocket of that hunk opposite? No you are correct, it is a design thing! After my mum had given me tube maps when I was a kid (was she trying to get rid of me?) I'd often doodle fantasy extensions on them and could sit for hours looking at the urbane delicacy of the balance between the station names and the lines or just the sheer stunning, timeless cleanliness of the Johnston typeface. There isn't much else to do on the Isle of Wight except watch the bacon slicer in the local co-op on a Friday night. At art class I painted a picture which tried to marry the diagrammatic view with a touch of geography. The dreadful mess proved to me why Harry Beck the designer of the original London Underground diagram in 1933 had been so successful but it got me place at Art College for sheer bare faced cheek! Since then I have always been fascinated by the graphic design ideas behind disseminating complex travel information in simple ways.

OutUK: As a Metro fan, you must be pretty upset about the current state of the London Underground...
Mark: It's such a great shame. Britain seems to make under-investment into a national sport. The first underground railway in the world opened in London 140 years ago and the trains still run through the same space between Paddington and Farringdon. Most of the system was built around 100 years ago with only a few extensions into outer suburbs and the Victoria & Jubilee lines completed in the last half of the last century.

Of course the new Elizabeth Line is a very welcome change to that, but sadly for decades the rest of the system has had little or no investment and basically is now rotting away. It might seem like it would be easy to fix but don't forget this is one of the oldest and busiest cities in the world with basements, utilities and sub surface waterways riddling the London clay. And other cites with older systems have had their fair share of shutdowns too - New York, Chicago and Boston have all had to shut whole sections for lengthy repairs. If you build such heavily used systems you must maintain them well.

OutUK: Some people might be surprised that a gay man would so interested in trains?
Mark: Really? I would have though the sight of great pounding machines thrusting into deep passages would be just the kind of thing that would appeal. I realise why gay men have fetishes for transport, sci-fi, showtunes or old films; we are generally carved out of fetishes for football, war games and swapping pictures of those things at an early age when we get an inkling there is something different about us. As our interests are raised in people of the same sex but then put down, heterosexual men (or guys that don't develop their homo side till later) are getting their teeth into something else. Thats when many gay guys suddenly develop a particular interest in Doctor Who, or collecting records, or movie diva's...all about the same time all their male mates (if they had that many) were off sniffing around girls.

OutUK: Do you think a gay man has a different appreciation of metro systems...maybe they're a vital part of a metropolitan/city lifestyle.
Mark: Some people think of rail commuting as monotonous, cramped or frustrating...but if you take a different perspective it changes completely. In most cases stations and trains are well designed aesthetically pleasing spaces. The environment is often adorned with highly sexually charged images on many of the ads. Due to the transient anonymous nature of the experience there can be very cruisy atmosphere of any busy place.

You are in an incredibly false, man made packed place - it's highly contrived - not unlike the experience of clubbing. Think of it like this; you are under 20 metres of earth piled above your head, you're racing through an iron and concrete tube in a metal cylinder, it's everyone all in together - there's no first class on most tube systems, the adrenalin is running, people are looking you over, checking you out, you are slightly losing your orientation, bumping up against fellow, sometimes quite sexy, passengers who you might never get the chance to rub up against or see again.....the lights occasionally dim or even go out....it's the ultimate fantasy - well until you wake up and find some doddery old drunk has thrown up your new trainers, but hey we can all dream!

OutUK: Finally, who's the book for?
Mark: It's a 136 page full colour hardback aimed at everyone from the casual city traveller to the design student, the transport enthusiast or trainspotter to the industry specialist. Its surprisingly absorbing leafing thru and seeing how each country and city has tackled the problem of getting such detailed graphic information over on a flat piece of paper. The maps are often beautiful and captivating. You find yourself pouring over them for hours remembering places you've been to or people you....'met'...or where you'd like to go or how each map differs from the next. Even the most sceptical people I've shown it to who expect it to be dull and boring have ended up saying stuff like..."Is Prague in there?" or "Did you know they have a subway in Rio?" or "my ex comes from Barcelona, thats the station where his family lived" - you see we're all so well travelled these days that we've had experiences all over the world so thats why this book has a universal appeal!