How does one cease to be eligible for a pension?

I only ask because of this odd exchange in the House of Lords. Lord Pearson has been highlighting for a while how former EU officials and Commissioners are in reciept of an EU pension that has as part of its conditions a rule about not annoying the EU, or indeed harming its interests (though the way they are going that should disqualify almost everyone working in the Berlyamont now).

Any how he asked about our dear Deputy PM, for of course not only was Mr Clegg a fornmer MEP, (whose pension is not covered by the rule) but he was also a member of Leon Brittan's cabinet, and was thus an official (whose pensions are covered by the rule).

So he asked in November the following

To ask Her Majesty's Government whether the Deputy Prime Minister, Mr Nick Clegg, receives a pension from the European Commission; and, if so, what is the annual amount of that pension, and whether the terms of that pension constrain his actions.

OK simple enough. To which Lord MCnally answered,

The Deputy Prime Minister does not receive a pension from the European Commission.

Well of course he doesn't thinks Lord P. He is still wet behind the ears, the guy won't hit pensionable age for decades. Lord P tried again, and the story gets, dare I say, odder,

To ask Her Majesty's Government, further to the Written Answer by Lord McNally on 15 November (WA 140), whether the Deputy Prime Minister, Mr Nick Clegg, is eligible to receive a pension from the European Commission; if so, when that pension will become payable; what will be its annual amount; and whether the terms of that pension constrain his actions.

Stop wriggling dammit and answer the question.
The answer came back

Lord Wallace of Saltaire (Whip, House of Lords; Liberal Democrat)

The Deputy Prime Minister is no longer eligible to receive a pension from the European Commission.

Eh? No longer. So he was, and now he isn't? And when did he decide to forego that pension, and why?