For an elderly non technical gentleman, reliable Pay as you Go with easy to see letters and numbers. No internet required. Preferably one that he can buy in Tesco! Thanks all.
Doro phones are repeatedly recommended here for their simplicity and ease of use for older people, so an obvious possibility here is . . .
https://www.tescomobile.com/shop/doro/5516
^^^ He probably won't find TTT's recommendation in a Tesco store though. Many (most?) items listed on Tesco Direct are only available online (at least for the next four days anyway, until Tesco Direct closes for good).
With such basic requirements, the IMO Dash (which should be available in larger Tesco stores) might be suitable. It's currently priced at £4.99. (OK, you have to pay £14.99 but that includes a £10 top-up):
https://www.tescomobile.com/shop/pay-as-you-go/imo/dash/black