By Ian Dunt Follow @IanDunt
Britain stands fully behind the Arabs as they struggle for freedom across the Middle East, Nick Clegg will say later.
The speech comes as Colonel Gaddafi's control over Tripoli disintegrates, with rebels now on the verge of taking full control over Libya.
"Today I want to make it absolutely clear: the UK will not turn its back on the millions of citizens of Arab states looking to open up their societies, looking for a better life," the deputy prime minister is expected to say.
"It is increasingly common to hear what was once hailed the Arab Spring now compared to a long, uncomfortable Arab Summer.
"The truth is: we cannot be certain exactly how things will pan out. But the direction of travel is set. And the fundamental forces driving these changes are here to stay.
'Youth, technology, a lack of opportunity and inclusion - factors which have collided to create citizens who want more, who know more, who aspire to more but who are denied it at every turn. This year that tension has hit boiling point."
Mr Clegg, whose party led parliamentary opposition to war in Iraq, will argue that by challenging Gaddafi Britain sent a stark message to other dictators in the region.
"The decision to support military intervention in Libya was not one the UK took lightly. Particularly not by those of us who opposed the invasion of Iraq," he will say.
"We went to Libya with a clear humanitarian mandate. And tens, if not hundreds, of thousands of lives have been saved since. But, we also knew that inaction would have threatened the Arab Spring as a whole.
"And now, as the Colonel's fate closes in on him, what message does that send to other dictators who ignore their people's demands?"
Strategists had concluded that the west's deep entanglement in Libya had actually encouraged Middle Eastern dictators dealing with popular uprisings, as it proved that they were unable to intervene anywhere else.
But with the regime now close to collapse that lesson no longer holds and many diplomats are hoping that events in Libya will encourage other states, most notably Syria, to back down in the face of the international community's demands.