AS Nick Clegg launched the Liberal Democrats’ manifesto today, it was impossible to hide from the fact that he will be best remembered for the broken promise on university tuition fees which he made in his party’s manifesto of five years ago.

Whatever pledges he was going to make this time round, the same question was bound to be repeated in millions of minds: “Why should we believe you?”

It is indeed a sad state of affairs that the same question will be asked of all the parties because “manifesto” is a word which has become synonymous with mistrust.

But of all the party leaders, the question weighs most heavily on Mr Clegg – and that is the price of coalition.

In amongst the widespread anger at that betrayal of trust, we believe there should be room for a degree of sympathy and understanding.

It is easy to forget the problem the country faced in the immediate aftermath of the last election.

A Government had to be formed and the Lib Dems met that necessity. Instead of descending into chaos that would have caused untold economic damage, Britain was given a stable Government.

The harsh reality for the Lib Dems, however, is that the party’s vital role in providing that stability will be overshadowed by that broken promise on tuition fees that forced a public apology from their leader.

Mr Clegg has now presented a new list of promises to the people. With no party likely to win an outright victory, he says he will seek to form a “coalition of conscience” that would not “lurch off to the extremes”.

The trouble is that he has the inescapable air of an unfaithful and unforgiven lover pleading for a second chance.

"I won’t let you down again – that's a promise” has a hollow ring to it.