Caporegime
So you worked your notice and had initially said that you'd do a second week as a sort of a favour, then backed out of it.
It seems quite a leap for him to get from there to breach of contract, unless your offering to do that second week somehow became binding.
Even then, I'm pretty certain he'd still owe you for hours worked in the notice week, and no breach could get around that, unless he could somehow show sufficient loss in the week you didn't work that then had to be recouped from your wages in the first week.
It seems quite a leap for him to get from there to breach of contract, unless your offering to do that second week somehow became binding.
Even then, I'm pretty certain he'd still owe you for hours worked in the notice week, and no breach could get around that, unless he could somehow show sufficient loss in the week you didn't work that then had to be recouped from your wages in the first week.

