1,000,000 * 1,000,000 = 1,000,000,000,000 = 10 ^ 12 = 1 tera-

Thus, a European billion has 12 zeroes.
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Not current usage in Britain - when British people nowadays speak of 1 billion, they mean one thousand million.
''Was it used that way?''

I think the UK treasury switched to using the US Billion in the late 60s or early 70s (It was under Harold Wilson anyway). Since then most people in the UK use a Billion to mean 1 000 000 000. To be sure, you should always say "a thousand million", or use the SI prefixes (That cost 5 giga-pounds).

Of course, most people can't conceive of the difference between a million, thousand million or a million million. You might as well say "a huge amount". That's why politicians often use comparative amounts like "this will be a tenth of what we spend on health". 
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So what's 1000 x 1 million in Britain? Thousand million. ''The dictionary says we should use Milliard, but I have never heard this in real life.''
Milliard is commonly used in Dutch, French, Italian, German and Polish.

Same even in Hebrew. And Billion is changing from 12 to 9 zeros to decrease confusion, I guess. -- NissimHadar

I can't really agree that it decreases confusion - the AmericanBillion usage flies in the face of what all European-derived cultures, including the U.S.A., used until about a century ago. It has caused confusion now continually for a century. In practice, the only sensible way to express what this family of quantifiers meant is to use the SI quantifiers. Besides, measuring the U.S.A.'s ''defence'' budget in teradollars has a certain resonance ...

Pity really; the European usage appears to make more sense: 10^(6''n'') as
opposed to the 10^(3''n''+3) of American usage (where ''n'' is the
number alluded to by the prefix mi-, bi-, tri-...).

I thought the European system was 10^ (3*2^''n''), which is very parsimonious with names and doesn't allow confusion between say a quintillion, a million quadrillion and a billion trillion.

''I've not come across that formula before, so I doubt that it's correct.''

Also the ''milliard'' usage is still common in UK financial circles where a billion is often referred to as a ''yard''.
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See also AmericanBillion...