The 67-year-old ex-leader of the Liberal Democrats was on passionate form in Eastney as he spoke to a crowd of 150 at the Portsmouth Festivities event.

But if the audience at the spiritual home of the Royal Marines thought they were in for an hour of nostalgia, they were soon put right.

'I'm afraid I want to talk about a gloomy subject, which is of an unprecedented scale for humanity in our time,' he said.

'I think we are unfortunately living in an age when a long period of stability is going to end, and what we will find over the next two or three decades is a massive concatenation of challenges.'

Lord Ashdown went on to discuss how the shift of economic power to Asia and the chaos of global money markets would force governments to scrabble for control in a new world.

It was powerful stuff and Lord Ashdown fielded questions about everything from the wars in Iraq and Afghanistan to the rights and wrongs of invading Zimbabwe.

Lord Ashdown, who served in the Special Boat Service and was instrumental to peace keeping efforts in Bosnisa in the 1990s, surprised the audience by warning against toppling Robert Mugabe just minutes after he had made the case for wars of intervention.

Terry Halloran, 61, of St Thomas's Street, Old Portsmouth, said: 'He has tremendous charisma. He's one of the best prime ministers we never had.'