Complex,I believe this may have a lot to do with the threat of...

Complex,

I believe this may have a lot to do with the threat of money laundering in the UK.

The Government was forced to tighten up the rules and regulations on British Banks following one or two scandals a few years back. We accused other countries of being very lax in this area only to find out we were no better with our banking code

I do not know if it is still the case but at one stage if you paid the equivalent of A$25,000 in cash into your own account. The Bank itself is obligated to notify the appropriate government department of all such banking transactions

I also believe a similar rule applies if you pay cash to buy a luxury motor car. Might be wrong on this one though

regards