Purely because of all the work and intricacies involved in running the country as leader, I could never be UK Prime Minister, without at least a degree in politics and all the experience needed for the job. After that, then yeah, I probably could. However, provided I had the right qualifications and experience (as always), then I could most certainly do a much better job as a Cabinet Minister than the current people. That's partly because I actually have good ideas, but also because I'd always run ideas past everyone with any experience and the right qualifications to answer sensibly before even thinking about bringing them to Parliament. And by that, I don't mean the general public (who wouldn't have a clue and would thus give skewed opinions), but actual people who are qualified to answer and who would give a realistic idea of what the effects would be. For example, if I was Health Secretary, I'd not just rush through reforms like Andrew Lansley is trying to over here right now. I'd have spoken to doctors, nurses, patients, hospital administrators, and so on, people actually involved in healthcare and with the experience needed to discuss it, before bringing the reforms to the government to vote on.
That, by the way, is another reason why I feel that ministers in Parliament should only be permitted (there should actually be a law about this, I reckon) to take on a role if they have the experience of that field already. For example, the Health Secretary should only be allowed to have that job if they have experience working as a medical professional. The Defense Secretary should have been a soldier or other military operative for at least some time before they're allowed to take on the role. And so on. Because that's the only way we're going to have politicians making the right decisions that really matter. A major failing of government is that most governments are completely out of touch with the actual needs of the people, and of the fields they are in charge of. Making sure the ministers actually know what should be done by making sure they know what they're talking about right from th off would be a massive positive step for actually having a successful, working, decent government.