I am all for the anonymity!
I would do the same as another person suggested and wait a while before telling family, so they don't know how much.
I would buy a flat or maybe a house in the city I currently rent in. Very nice but not extravagant. I have no desire for a massive house. I would get a dog. Maybe two.
A good chunk would go to my adult children, not sure yet in what form. A smaller chunk to my brother, maybe £1 mill.
I would send money anonymously to friends, including some people I'm not really in touch with any more. Probably in varying amounts from £250k to I dunno, £1 mill.
I would like to do something to support others, specifically trafficked individuals/people finding themselves used as slaves and women in forced marriages that can't find a way out.
I would also sink a 5 figure sum into an arts project that I'm involved with that hasn't been able to get off the ground due to funding issues.
And I would invest a chunk to live on. Enough so that I'll never have to worry about money, and I'll be able to travel as much as I like, in luxury. And maybe fund more projects. In fact I might set up a trust for that.