PieEater I don't understand how these clauses in contract perpetuate.
If it was in Harpers original contract, surely it would only have been valid for the duration of that contract. Once he signed a new one then the clause would go. The only exception would be if he kept extending the original contract on better terms, in which case someone screwed up.
Presumably there are two contracts in a transfer. One for the player and one between the selling club and the buying club (which contains clauses such as this one). And I guess this lasts as long as the player remains with the buying club.