@Soontobe60
Imagine someone who is, say 30, and is mortgage free with a 2m inheritance. I expect they hope to live for another 50 years. Even without a mortgage they probably want an annual income of 30k taken from their 2m. Given an inflation rate of 5% annually, that means in year 2 they need 31.5k, year 3 33.073, year 4 34.728k and so on. By year 10 it’ll be over 45k. By year 50, they would need over 344k to live on.
Their 2m will have run out well before that though.
This needs some adjustment. First, the average annual inflation rate is under 1.8%. Which means in Year 50 it would be 72k to live on.
Also, this is assuming the OP touches the capital, which she shouldn't. It should be invested and the interest used as income. If she wanted to live modestly, she could live on the interest for the rest of her life (though it might get tighter at the end, at which point she could touch the capital).
That said, OP, the longer you can have the money sitting in the bank and generating compound interest without touching the interest or the capital, the better.
So, if you have a 5% interest rate, leaving the money alone for 10 years should generate about another £1.25 million, without any additional contributions. This would mean that you could 'retire' in your early-mid 40s with £3.25 million, which would up the interest from around £100k to around £162k per year, which is a big change in lifestyle.
The extra money could, for instance, fund your children's university with no debt for them. If you have two in uni at once, you're looking at about £40k/year, minimum, for fees and room/board. On an income of £100k, that might be a pinch; on an income of £162k, it really isn't.
I know these sound like astronomical sums. And it also doesn't touch on the moral/ethical/intellectual questions. Or personal questions, like do you hate your job. But in terms of sheer math, I'd get a good financial manager, stay on my salary for another 10 years (maybe switch to part time if I had to, touching as little of the inheritance as possible), let the interest accrue, and then re-evaluate in a decade.