@Andrew

The reasons for the different analogue picture formats are mainly technical.

You watch on a 625 line in the UK, because the original time base was kept in step by the AC signal, 50hz. The USA has a different frequency (60hz), which means the time base runs faster. There is a limit to the amount of picture information you can get across on the carrier signal, so as the USA time base runs faster, you can't send as much information, so less lines.

These days with accurate oscillators, you could pick any time base you like, but of course it has to be compatible with all the existing gear, unless you really bite the bullet and invent a new format like HD.

NTSC was the first colour encoding system the engineers came up with, but as anyone that has ever seen the results, it tends to drift about a bit (okay, these days it's better, but that's thanks to a hell of a lot of clever modern electronic fixing the inherent problems), NTSC was even nicknamed Never Twice Same Colour! The UK engineers stuck as the R&D, convinced there must be a better way, where the colours would be more stable. PAL was the result. Hence an NTSC signal on a PAL TV produces a picture, but the set cannot decode the colour information, and vice versa.

There was no anti-competitive reason for it at all.

SECAM, well that's just the French isn't it. They wanted to protect their TV manuafacturing industry, so invented their own format. Incidently a lot of eastern block countries used SECAM too, because that way the only "free" world country they would be able to sneak a look at would be France, they certainly didn't want Eastern German residents seeing life on the other side of the wall.

So now we just have to decide exactly which side of the wall the BBC are putting us on!