'Good news! Mutassim Gaddafi has been captured!'

The gunfire started just as I returned to my hotel last night. I called down to Mohamed on reception. “Good news!” he said. “Mutassim Gaddafi has been captured.”

At that point they opened up with what sounded like anti-aircraft guns and a carload of young men raced past shouting “Allah Akbar!” and shooting their kalashnikovs out of the window. I retreated from the window. Libyans have a distinctive way of celebrating and it involves a lot of ammunition.

Mutassim was Gadaffi’s fifth son, and served as his national security adviser, with his own special forces brigade, which led the former government forces in Gadaffi’s hometown of Sirte. He was the main rival to Saif Gaddafi, the second son, as both young men believed they should be the successor to Colonel Muammar Gaddafi.

Mutassim tried to poach reformist academics who worked for Saif – one man told me how terrified he was when Mutassim offered him a job, because he feared that he might end up in prison for saying no. The two brothers are known to have had furious rows.

Mutassim had a reputation as a playboy and a whiskey drinker – the most extraordinary account comes from his former girlfriend, a Dutch model, who says he once told her he spent US$2m a month on flying round the world and having fun.

When she last saw him, just before the fall of Tripoli in August, he was apparently bearded and stressed, surrounded by unsmiling 16-year-old guards. His days of hard partying were over – he was now on the run.