Yes, Waitrose should have a duty of care towards its employees and Mr Smith had (apparently) had a previous warning.
However, that duty of care, especially towards a partner who may be on the autistic spectrum as Terribull posted, should mean that they should have found him alternative employment in a non-customer facing role as I suggested earlier.
I still think they were heavy-handed in dealing with this, and it seems to be against their well-publicised description of how their staff are not just employees but partners, owners, with a voice in business decisions, etc etc.
www.jlpjobs.com/about-the-partnership/being-a-partner/
The "Partnership" has cut 3,800 jobs in a year and plans 11,000 more job cuts over the next five years. Well, 10,999 now Mr Smith has gone.
It really isn't worth the paper it's written on, or the space it takes up on the internet.
I must say the staff at our nearest Waitrose are lovely but they have made more tills self-service.