Following the Bear Scotland v Fulton case, if an employee can refuse overtime, does this need to be included in holiday pay?

The decision of the EAT in Bear Scotland received much media coverage, but attention should be drawn to the three separate definitions of overtime clarified by the EAT:

(1) ‘Non-guaranteed overtime’: where there is no obligation on the employer to provide the overtime but where the employee is obliged to work, if offered overtime;

(2) ‘Voluntary overtime’: additional work which the employer asks an employee to do but which the employee is free to refuse; and

(3) ‘Compulsory overtime’: where the employer is contractually obliged to provide the overtime hours and the worker is contractually obliged to complete.

Voluntary overtime was not dealt with definitively by the EAT in the case, and so