Hi Esmerelda, there are lots of moving parts with this, hence would need independent advice given your specific situation.
As an indication, I would be looking at the risk-free rate of return - if we focussed on the UK 30 year GILT, this is currently giving a yield to maturity of 3.76% - so if we invested £2mn into this, this should provide an indicative annual income of £75,200 per year for the next 30 years
Happy to discuss in more detail if you like:
jaips.rekhi@ccfpllp.com, mobile 07826 101718. I live in Balham