1/260th held the Court of Appeal in Hartley v King Edward VI College, not 1/365th.
The appeal arose from a County Court claim by three striking teachers, alleging that their employer had withheld more pay than it was entitled to in response to a day's strike. This was not a deduction from wages case as a 'deduction' presupposes an employer not paying a sum which has been earned. Here the sum was never earned, the dispute being how to calculate it.
The College based its calculation on a notional 5 day week, 52 weeks a year, making the sum 1/260th of annual salary; the teachers argued that the nature of their contract and section 2 of the Apportionment Act 1870 meant that pay accrued equally from day-to-day, and the sum to withhold was the smaller 1/365th. The Court held that the sum withheld was to be calculated on the basis of the contractual terms, and noted that although the Apportionment Act applied, it did not require the principle of equal daily accrual of salary to be applied: 'provided it is plain from the terms of the contract that the principle of equal daily accrual is not intended to apply, that should be sufficient to exclude the principle even though there may be difficulty in resolving precisely how the pay is related to the work performed' (para. 43).
It was noted that the cost implications of the judgment across the education sector would be around £300,000 per strike day.