I've always found a lot to admire about Jamie and his various eating healthy campaigns, particularly with regard to overhauling some of the food dished up in schools. I think he was very sincere in his endeavours.
However, I take issue with his comments about his restaurants going under due to Brexit. Brexit aside having eaten in Jamie's several times the food was pretty awful and other people I have spoken to who have eaten there said the same. Like a lot of celebrity chefs who want to conquer the high street, I think he overstretched himself and just expanded too quickly, far too many balls in the air. Marco Pierre White who is an adversary of his, so could be accused of having an axe to grind, but imo quite rightly pointed out that if Brexit was a factor then all restaurants would go the wall and poor service was a regular complaint with patrons. There have always preferable high street alternatives with similar costing menus to Jamies such as Cote and Bills, who are far superior imo and both seem to be thriving. Sometimes a famous name is not enough if the food and service are pretty poor.