[Note that Jon Speelman also looks at the content of the article in video format, here embedded at the end of the article.]

Years ago, when ChessBase first appeared, I amused myself for several months by trying to crack the old cb3 data structure. It was encrypted, and initially, I managed to work out the headers (names and tournaments) and write a utility to change these en masse.

It was considerably later that I was able to crack the moves, partly because they were also encrypted (by the first three odd primes: 3, 5, and 7, if I recall) and partly because the old move generator had a bug: the en passant "flag" wasn't reset properly.

This meant that moves such as a5xh6 en passant were in the list, as indeed were en passant captures where a piece arrived in front of the pawn – Bg4xf3 ep, for example. By playing with a hex editor, it was possible to create games in which these moves were "played" and strange phenomena appeared visually on your screen.

Sadly, I can't find these anymore – and I rather doubt whether the latest versions of ChessBase would be so accommodating – but there are plenty of strange moves played in real chess games, and I thought today we’d look at some, starting with the little bug which set me on this path.

Black has just played Rb6xb2. Can you see White's clever response?

To some extent, c4 "feels" like it should be subject to an en passant capture, and I've added a real en passant capture (which I had here a while ago) albeit in a fairy chess setting, in which with the aid of a so-called nightrider, White delivers a triple checkmate!

MV-L's clever c4 trapped the bishop, and I'm concluding with three more or less famous examples (my own game is pretty well known and the other two are absolute classics) in which pieces were trapped voluntarily or otherwise and escaped, or in one case didn't.

I'll be back on August 4th. Please send me any suggestions if you like.

Master Class Vol.17 - Boris Spassky

In this video course, experts including Dorian Rogozenco, Mihail Marin, Karsten Müller and Oliver Reeh, examine the games of Boris Spassky. Let them show you which openings Spassky chose to play, where his strength in middlegames were and much more.

Links

• Previous column: May miscellany
• All Speelman’s Agony columns