I'd put it in simple low-risk, low-return investments probably. However to be honest if I only won £42m then not much would be left after sorting out family and initial spending on property. Buying a 'nice house' in a good part of London costs millions and while you said we must assume no kids it is quite hard to think in that way.
As for people winning lotto and running out of cash, that's very easy because the jackpot is often quite small these days. Again, initial expenditure on property, cars, family etc can run into millions, and then would be very easy to spend hundreds of thousands every year just on living life (holidays, nice clothes, furniture nice gadgets etc). Some people also are 'addicted' to acquiring new things in the sense that they will replace said items very quickly i.e. new car every year, new furniture etc etc even on much smaller payouts. In other words they buy items with a high rate of depreciation on a frequent basis so capital is diminished quickly even before you take into account spending on 'experiences' that leaves you with no material asset at the end.
edit: when considering this sort of topic I often like to try and come up with an amount that would be the minimum amount that would have a drastic impact on the way I live my life outside of work. It is quite scary really because that number has grown over time to the extent that basically the fabled 'millionaire' life goal is actually pretty underwhelming. If I won a million quid basically that would let me buy my mother in law a house, buy us a new house and that would be it. Unless I did something drastic like quit work and stay in our current house, but not sure I would be confident doing that in terms of long-term provision for my family i.e. the interest on a million quid after tax (assuming basic cash investments) is pretty paultry really.