In Industry & Commerce Maintenance v Briffa, the employer gave Mr Briffa one week's notice of termination of his employment. It required him to take 4 days holiday in his last week to use up his outstanding entitlement.
An employment tribunal held that the employer was in breach of Working Time Regulations 1998 Reg 15 which requires that an employer must give notice of holiday dates "double the amount of time to be taken". Since Mr Briffa was not given 8 days notice of his holiday, taking it could not legally be required of him. He was awarded 4 days' pay in lieu of the 4 days' holiday.
The EAT allowed the employer's appeal. The original tribunal had totally overlooked that the basic requirement in WTR Reg 15 can be varied or excluded by a "relevant agreement". In this case there was a contractual term which covered the position and was legally enforceable between the parties. This was a "relevant agreement" under Reg 2 and it overrode Reg 15.
[Thanks to www.emplaw.co.uk for allowing me to use their summary of this case]