The guy is an absolute legend and deserves to be Knighted but there is only so much money to go around and if Boris is wasting it on completely pointless letters it's an insult to this guy and all those who have donated.
As far as I am aware UK debt is just shy of £20000000000000, passing no comment on that total, but £6000000 is in the grand scheme of things P**s all, and if it got a message to only a small % of the country that dont follow current affairs online or tv ( more people fall in this group the you would expect) it potentially has saved lives, and personally a few saved lives is worth a penny or so on my future tax to pay for the letters, if you feel it was wasted money then that is really not a great reflection of character.