What I did with my lump sum: put £20k in an ISA with a fund supermarket like Hargreaves Lansdown (but not necessarily them) and invest it in low fee tracker funds like Vanguard. Choose a mixture of markets to track, UK, US, European, emerging markets, and maybe buy some bond funds as well to spread the risk. Every year, pay another £20k slice into the ISA. If you’re quick, you can get the first slice in before 6th April, and then the next one immediately after. I also gave £20k/year to Mrs G to put in an ISA in her name, so it didn’t take long to get it all tax sheltered.