By 29 February he would have already earned an entitlement to relief. If however a substantial bonus became payable to him on 31 March 2000 in relation to the period spent abroad, he would find the relief denied to most of that bonus, because it was paid on or after 29 February. This is so notwithstanding that it may have been earned prior to that date. On a more minor level, the choice of introducing the restriction by reference to payments on or after 29 February meant that it caught February payrolls, where these were paid on the last day of the month. Although not formally retrospective legislation it is in effect retrospective, given that salaries are normally paid in arrears.
Retrospective legislation is always objectionable.
In the present instance it is difficult to see any justification for this approach. It is difficult to understand the thinking behind these restrictions. Salaries cost an employer money, share options do not. They should not be enjoyed by the very high earners. Old attitudes die hard.