Speaking at PRWeek's PR and The Media conference on Tuesday, Kelner said: ‘Branson took the story away from being an institutional and public disaster and made it one about the heroism of the train driver.'
An 84-year-old woman died and 22 people were taken to hospital when a Virgin Pendolino train derailed last Friday in Cumbria.
Branson, who cut short a family holiday to attend the scene of the crash, has been widely praised for his response.
In a separate session at the conference, BBC College of Journalism editor Kevin Marsh argued that broadcasters should cease to see viewers as a mass audience that they can control. ‘Content will no longer be "pushed", but it will be "pulled" through searches by users,' he said. ‘Viewers are not rejecting "big media", but are choosing to use content their own way.'