Does anyone know how likely it is than an employer would taken action if an employee resigned with immediate effect and didn’t work their 4 weeks’ notice? If it makes a difference to your answer, this is a barely-over-minimum-wage job, as opposed to a highly paid professional role.
For context, the employee committed gross misconduct and decided to resign before they were sacked, so I’m surprised the employer has mentioned breach of contract, I would have have expected them to jump at the chance of getting rid of the employee quickly.