Nick Clegg was forced to abandon a photo-call outside the Houses of Parliament, after a protester doggedly kept interrupting the deputy prime minister.
Protestor Bill Maloney shouted repeatedly at Clegg who eventually deserted the planned photo-call which was to promote a tax cut announced in the budget.
Senior Lib Dems had planned a media appearance with a banner claiming Lib Dem credit for the announcement in George Osborne's 2014 Budget that the lower threshold for tax would be raised to £10,500.
Protestor Bill Maloney shouts during a live TV broadcast by the BBC News Channel
Maloney gestures as he shouts at Deputy Prime Minister Nick Clegg
This is how it should have gone, before they were interrupted
The BBC's Norman Smith told viewers on Wednesday afternoon that the Lib Dem leader "had had to abort, because we were here to here for a little photo-call the Lib Dems have organised to flag up what they say is their key tax measure, which is raising the lower threshold."
But, he continued: "Mr Clegg was there, all his Lib Dem people were there, but the whole thing had to be aborted because a few protesters came along and spoiled the occasion. So Mr Clegg has gone over there."
"I don't know if he'll be coming back in the near future," Smith added, mournfully.
As Smith began an analysis on pressure in the coalition for parties to claim credit for popular policies, in burst Maloney. "International paedophile rings are operating in this country, now!" he said, shoulder-barging Smith. "I just asked Nick Clegg a question.."
But BBC News viewers never found out what that question was, with Smith apologising and cutting the feed.
They did, however, find out what the deputy prime minister was planning to say. He later told the BBC that the coalition has "over delivered" on the Liberal Democrat's flagship policy.
"I'm extremely proud of what we've presented for savers, for workers, to make sure that we keep energy intensive industries in this country employing thousands of people," he told the broadcaster.