Fellow Brits, in one word, what is the biggest problem facing our country?

Excessive government regulation of the economy. The government has had immense regulatory control over all aspects of the economy since the war, with some variation, and the results are absolutely abysmal. We have been the sick man of Europe for most of that time with our economic advantages reduced to dust, and the periods of success have largely corresponded with strong global economic winds or local periods of deregulation. I used to believe in the post-war settlement, and it does sound good on paper, but it failed. I now believe it was the biggest mistake in this country's history. We didn't even make twenty years before we were drawing on IMF loans in the 60s, and then came the bailout in the 70s that ushered in Thatcer, The government is not capable of running the economy to the degree we pretend. The civil service will run any business straight into the ground if given power over it.