The problem employers have now got is that they cannot use tried and tested excuses of not allowing WFH for their employees. The biggest excuse in my opinion was 'it is not cost effective, having to install extra phones for work usage, paying for the phone line and electricity usage during working hours'. The pandemic has proven employers wrong in any excuse they try to use to prevent their employees from WFH.
Employers cannot force their WFH employee's back into work unless the employer has a strong justifiable reason to do so because otherwise the employee would be able to raise a grievance against the company as set out in the company policy and procedures for employee's. If the company was to sack the employee for refusing to return to work, the employee would be able to claim unfair dismissal because if the employee has been able to do everything that the employer expected of them whilst WFH, the employer would now have to justify why the employee is now required to work from the company premises.
Unless an employee's work contract specifically states that their place of employment is the employers premises the employer cannot get the employee for breach of contract.