I think this is deeply illiberal. There are some cases where bans make sense like the XXL Bully dog ban that has been mooted. But I don't think the government should be able to decide what an adult puts in their own body.
My dad was an oncologist for years and he said that one of the reasons we're having trouble in the NHS is that people have stopped smoking. Unfortunately if you are stricken with lung cancer then your prognosis is not good - and while this is a tragedy - you potentially could end up costing much more money in terms of social care and hospital visits if you carry on to live to a later age but get stricken with a more complex degenerative disease.
This is disappointing. Honestly I has found Sunak to be a relief on the whole after our previous few Prime Ministers, probably on par with Therasa May. In my opinion this is a cynical attempt to steal a policy that Labour's Wes Streeting was going to announce soon in order to take the wind out of his sails.