Collectors of rare comic books are often regarded as geeky by those who aren't part of the obsession. But in fact comic book themes are rarely out of the public eye, with the movie Kick Ass only the most recent to draw inspiration from superhero adventures.

Whether in the latest Batman movie, animations such as The Incredibles or the TV show Heroes, a constant stream of references to heroes with spectacular or unearthly powers is always on offer.

Perhaps that's why the market in original comics has remained so strong over the years. The earliest superheroes' outings, assuming they are in good condition, have shown no signs of losing their value - quite the opposite.

The Man of Steel on Action Comics #1

Back in February, a copy of Action Comics #1, graded 8.0, was the first to reach the seven  figure mark, selling in a private sale for exactly $1m with the assistance of ComicConnect. The comic presented Superman (and the caped superhero as we know them) to the world for the first time.

The sale threatened to overshadow Heritage Auctions' much hyped March sale of a pristine copy (again graded 8.0) of Detective Comics #27 (introducing 'the Bat-Man') which was taking place just days later, and which had then received internet bids of around $300,000-400,000.

To Heritage's pride and relief, the Caped Crusader squeaked past the Man of Steel to become the world's most expensive comic, at a cool $1.075m.

Detective Comics #27 - introducing Batman

Comic fans could be forgiven for thinking that that record would stand - at least for a year or two, but just a few weeks later on March 30 the record was not just broken, but smashed by another copy of Action Comics #1.

This issue, graded at an extraordinary 8.5 - again through ComicConnect - and almost certainly the highest graded comic of its era, was purchased by a private collector for $1.5m - just shy of making it the first �1m comic.

Big comic sales are not limited to these two issues from the DC Comics family, however - there are a number of comic issues on the market for six figure sums.

Last December, one of Marvel's most difficult issues from the Silver Age (dating from 1956 for about 15 years - the Golden Age is considered to run from the late 1930s through the 1940s). A high grade Incredible Hulk #1 brought $125,475.

There are also many comic books on the market for four or five figure sums - for those with pockets less deep than, say, Bruce Wayne's.

Comics are being used explicitly as an investment more and more. The proof of this may be found in an unlikely case in America last year where a busted drug gang were found to be in possession of a number of high grade collectible comic books.

Sadly, this was not a sign of the criminals' softer sides, but an ironic example of crime-fighters being used to launder money. Fortunately, most investors are much more reputable.

Flash Comics #1

In some cases they don't even have to initiate the sale. Between the two most recent record breaks, an extraordinarily high-grade issue of Flash Comics #1 was bought for $450,000 from a collector who had paid $273,125 for it just a few years earlier.

The buyer tracked them down via Heritage's new service to offer to buy once more things the auction house has sold.

Heritage's own David Tosh predicted in his interview with us that collectible comics were the best investment around, and he could hardly have predicted just how right he was.

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