Why is the uk domain .co.uk, when other countries don't have the .co (e.g. .fr, .de)?

Just wondered why this is. google.fr, google.de, yet in the uk we have .co.uk, rather than google.uk. Anyone know the history behind this? In addition – i’m keener to know why the uk doesn’t release it, when others do. what is the history and what were it’s intentions http://bit.ly/l5rf5N