What is the greatest mistake in British history?
While many Americans probably think that upsetting the colonists with "taxation without representation" was a huge mistake, it's impossible to think that England could have kept all the colonies to this day. The US would be like Canada is to the Commonwealth.
The only colony in the New World that remains a part of the country that owned it is French Guiana, which interestingly is makes it the only EU member in the Americas (and the biggest member outside of Europe).
As for appeasing Hitler, that was a colossal mistake that cost many lives. Chamberlain waving the Munich Agreement to ecstatic Londoners showed how clueess they were to the dark clouds gathering over Germany. Had they taken a harder stance against Germany they might have prevented the blitzkrieg and perhaps setup a better line of defense in France rather than having to fight for their lives over their own skies and endure night upon night of bombing because of France's capitulation.
So, what do you think Britain's biggest mistake was?
Although looking back with the power of perfect hindsight it seemed obviously wrong, the appeasement of Hitler seemed almost inevitable considering the conditions of the day. I doubt the blitzkrieg could have been stopped by the inclusion of the British. It'd have either ended up like Dunkirk again or they'd have dragged it out for more losses than was historical and then folded again. Britain was not ready for the offensive like Germany was and even with their help a defence of France would be inadequate. This was not the old trench war of the last generation. They'd have been battered back into a defence on the islands again. The Battle of Britain allowed them to dig in and start building up again. It bought time for them. Time and delaying tactics was what they really needed to get the Russians and Americans on board before they had a hope of victory.
The biggest mistake would be the loss of the American colonies, I would say. Although they grew stronger and much larger after it, it could have been resolved in a better way and so was preventable and could have worked out much better in their favour.
The rest on that list I wouldn't consider mistakes or are obviously silly options.