If we project her lifespan as 50 more years and assume the UK population stays stable at 70 millions, that works out at 3835 and a half lunches per day.
I seriously doubt as a public servant she'd be a beacon of efficiency so I don't think she'll do more than 2k a day if this happens.
Maybe she skips the main on every other lunch?
The most lunches I’ve ever eaten in a day was 7.
What's the biggest restaurant in UK? How many people can have lunch with Adele at the same time?