The late ex-PM, Margaret Thatcher, was a formidably hard worker with an acute memory (reinforced, I was told, by the simple but laborious expedient of diligently doing her homework, on this as on so many other topics – reviewing notes on people she could expect to encounter at any given function or meeting). She is said to have worked at hours when most others would sleep, and as a consequence to be frequently better informed on the topic at hand than her interlocutors expected.
I have no doubt that she cultivated, on this basis, an air of infallibility. It also doesn’t do, of course, for a politician to appear uncertain or easily swayed on any topic whatsoever. Certainly, her public persona was of someone who, while prepared to listen to advice up to a point, was unlikely to be dissuaded by it from the idea that she knew better.
Here’s where I think the hard work and diligence run into a problem. If you are certain that you usually know better than everyone around you, but behave as though you always know better, the consequences when you are wrong are that much worse. If you are incapable of recognising the times when it’s vital to take advice and act on it, it’s a lose/lose: you make a bad decision, you undermine your own credibility, you discourage further advice, you alienate qualified and intelligent advisers, and you waste the available expertise. This becomes a vicious spiral and, politically, I think we saw where it led.