Please please contact a professional. Speak to a Chartered Financial Planner, preferably interview 3. Ask them how many clients they have with over £1M invested, what is their experience is of generating income from investments? Ask them what their strategies are, how they dealt with 08 and 2020! This is a strategy tailored to your needs, one of which is to support your DF. Ask to understand what basis their advice is based (which modellers and data - not guess work and ‘experience’)
£1m could as a very rough starting point give a guide income of around 4% - sustainable income that will last over time. However how the incidents such as 08 and 2020 are dealt with and the strategies employed will impact this figure. There is research on this, data that shows how this plays out going back to 1900, there are Monte Carlo modellers that can help us look forward. It could be more and it could be less, what it never is, is a straight line of performance (anyone that uses a straight line cashflow modeller is dangerously deluded, or plain stupid).
Look for straightforward language, reasonable fees (ask for a FULL list including fund charges), hesitate when they tell you they use DFM’s (discretionary fund managers) - get the data.
If you are in London you have a lot of very good advisers. I would also suggest that you look for a woman. As an industry the women are thin on the ground, but they are far better at the soft facts and the planning not just dick swinging their fantastic investment skills (which isn’t their job) - my opinion. Women are better qualified too - fact. (more women are chartered as a proportion of the profession) .
Without wanting to offend the whole board, but what I would NOT do is take advice on an internet board, it’s good for a few ideas to explore, but I constantly read lots of inaccurate information that is misleading.