Max out tax free allowances, ISA's, Pensions, Property is a good idea but speak to good real estate agents who will handle the property rentals for a small commission.

Investing in index funds is a great idea and nows a slight downturn so average into them.

Speak to a good financial advisor, yes they will recommend investing, speak to them about your risk tolerance, there are relatively safe investments, if you really want safest route, drop it all into Bonds, the issue is inflation (which is very high right now) will erode the value. Definitely want to be wary of Investing in individual shares.

If you've spoken to good ones they won't be surprised by the amount of money but will always be able to take the emotion out of investing and try to grow your wealth as that will keep you happy & paying their fees.

Remaining wealthy is about how much of the value you can keep.