Turns out the union was right. We had all assumed that Sam worked for us, but in fact for the last 17 years we have been paying £500 a day for him to Temps-R-Us. Their account has been going direct to Creditors every month and they have dutifully paid it.
Sam was philosophical when I called him in to say goodbye. After all, he has his cottage in Cornwall, flat in Venice, apartments in Corfu, row of houses in Tunbridge Wells and 30% of a holiday village in the Maldives to look after.