Four men got out of the van and pretended to exercise, but when police arrived a gunbattle erupted.
Mr Udayshanta recalls: “I heard the crack of a gun and I pulled my pistol and fired back.”
The white vans are the vehicle of choice of hit squads who make opponents of the powerful disappear. Mr Udayashanta had been involved in a dispute with another ruling party MP over a business deal. His brother had already disappeared – dragged away a month earlier, he says, by men in a white van.
But things went differently back in March. Mr Udayashanta and his entourage surrounded the men from the white van and captured them. Eventually, at gunpoint, the men acknowledged who they were: Sri Lankan government soldiers.
In a country where people had hoped the end of its bloody, long-running civil war in 2009 would mean a return to normality, the open secret of the white vans has come to exemplify the terror felt by anyone who falls foul of Sri Lanka’s rulers.
Mr Udayashanta’s case and that of Sri Lankan-born Australian citizen Premkumar Gunaratnam – who claims he was freed from abduction after pressure from Canberra – have provided the first hard evidence of the government’s involvement.
But neither case has done much to overturn Sri Lanka’s culture of impunity. Police said the soldiers who got into the gunfight with Mr Udayashanta were actually searching for deserters.
Rights activists, opposition MPs and journalists say top officials send abduction squads in white vans to “disappear” opponents, activists and criminals. White vans are parked in front of homes, in clear attempts to cow critics into silence. The citizen journalism website www.groundviews.com says 58 people have disappeared over the past nine months. In at least 22 of those cases, witnesses saw victims forced into white vans.
Mr Gunaratnam, a former Marxist guerrilla, who was active in an armed rebellion in 1988-89 and now lives in Australia, had returned to Sri Lanka to help start a new political party when he was snatched in Colombo.
“All this happened within a few seconds… they stormed in and abducted me,” he said from Sydney. “They tortured me, interrogated, humiliated me.”
His captors questioned him about the new party and whether he had links to the separatist Tamil Tiger rebels who were defeated in a civil war in 2009. Their manner suggested military backgrounds, he said.
Back in Australia, his wife Champa Somaratne and green party senator Lee Rhiannon, sounded the alarm. A few days later, his captors handed him to Australian officials.
Large-scale disappearances were first reported in 1971 when Marxist rebels launched a rebellion. The second Marxist insurrection in 1988-9 saw scores of young people abducted by paramilitaries, with bodies later found burning by roadsides. Abductions and killings were also linked to the Tamil separatist war launched in 1983, especially its final years.
Though those conflicts have ended, the abductions have not. Victims in the past year include politicians, businessmen, suspected crooks, former rebels and even a fortune-teller.