When Alexandre Mouradian, a top London trader at the French-owned Tradition Securities & Futures, took his employer to court for allegedly failing to pay his full bonus, he provided a peek into the opaque world of investment banking pay.

Figures he gave this month to the Court of Appeal, which is deciding how his case should be heard, show he took home a ￡1.32m bonus for the second half of 2006, on top of a ￡300,000 salary. Mr Mouradian, who kept for himself 92 per cent of the total pool set aside for his eight-member exchange traded options team, insists he is owed an additional ￡92,571 from broking fees.

The interdealer broker, part of Compagnie Financière Tradition, is fighting back, so the case offers a rare window into how employees in financial groups scrap for their share of the year-end bonus pool. By investment banking standards, the bonus paid to Mr Mouradian was far from unusually large, but at more than four times his salary it was crucial to his overall compensation. Now this system of backloaded pay that is highly dependant on revenue is under threat as never before.