With ease and measure, Grant, who has replaced Allan Biggar, leisurely talks his way through a career that has seen him come within a whisker of entering parliament, thrown out of Crufts and declared Great Hero of Nigeria's Ogoni people.
Growing up in a politicised household, Grant says, provided a defining moment in his career.
When in 1968 Basil D'Oliveira was banned from entering his native South Africa as an England cricketer because of the colour of his skin, Grant's passion for sport and his growing interest in politics collided and prompted him to join the Young Liberals.
'I've only ever been liberal, whatever name the party has chosen to describe that as,' explains Grant. 'Britain was a difficult place as you came to the end of the Seventies. There was a lot of social discontent, unemployment, and the far right were on the march.'
This interest in social justice kick-started his career, when a report he filed independently in 1979 on racially motivated violence in Britain got blanket national coverage.
He says his media relations strategy in those days was to say 'yes' to everyone, despite the fact that he was operating a one-man band from his bedroom in Ilford.
Grant quickly learned how to manipulate the media and was widely tipped to pull off the upset of the 1987 general election when he stood in Southend West for the Liberal Party - his second stab at office. But, admits Grant, all these skills could not alter the fact that the party was in decline and he lost. 'I'm proud that Thatcher was forced to make her last election speech in Southend,' is his self-consolatory stance on the matter.
Ambassadorial in manner, Grant has never been shy of using shock tactics for campaigns in which he passionately believes. An animal lover and staunch supporter of a fox-hunting ban, he presided as director of campaigns and PR over the RSPCA's 1989 ad which depicted a mountain of dead dogs, a campaign to introduce dog licences which got him thrown out of Crufts with the media looking on.
Given this rebellious streak, one wonders how he can fit into an agency popularly perceived as the mouthpiece to big business. PR consultant Simon Bryceson's personal and professional relationship with Grant began almost 30 years ago as student union presidents. He believes that 'as Gavin has grown older, he's come to see the significance of those stunts being in their power rather than their excitement', but is still driven by a desire to affect change.
Anti-corporate publication Toxic Sludge Is Good for You puts B-M at the top of the list of PR agencies to which 'evil' corporations turn in order to cover up misdeeds. Grant's reaction is quick, forceful and dismissive: 'They're just wrong.'
He asserts that logic and rational thinking dominate firms, but there is an emotive side to most comms challenges. One of the first campaigns he led for B-M was on behalf of the Alliance for Consumer Fire Safety to counter attempts to ban flame-retardant chemicals, which Greenpeace claimed were carcinogens.
'I'm not a scientist, but I can understand the implications and outcomes.
Since we've had these chemicals and materials, you don't have the terrible furniture fires that wipe out whole families,' he says.
Grant even points out the progressive actions B-M client Philip Morris has made to the smoking debate, before adding: 'I don't want to live in a nanny state, that's why I'm a liberal.'
There is no doubting the emotion and barely contained anger that characterises Grant's recounting of his campaign at The Body Shop to highlight the plight of Ogoni people at the hands of Nigerian dictator General Sani Abacha.
Despite protestations that his role was 'minor', the plaque that hails his status as an Ogoni chieftain takes pride of place on his office wall.
1979 Organising secretary, All-Party Joint Committee Against Racism
1980 Joined Liberal Party
1987 Campaigns director, Council for the Protection of Rural England
1989 Director of campaigns and PR, RSPCA
1991 Director of public affairs, Association of Unit Trusts and
1994 Director of global corporate and public affairs, The Body Shop
1999 Chairman of public affairs, Burson-Marsteller UK
2005 Chairman, Burson-Marsteller UK