'Diagrams help you visualise. I do use pictures to communicate ideas and for that I make no apologies,' he says.
The gently spoken science scholar rubs his slightly jet-lagged eyes.
It has been five days since he became Edelman's sole London CEO - a post he had shared with Nigel Breakwell - and a crammed schedule has already included one trip to the US. Smith refuses to be drawn on Breakwell's quick exit last month (PRWeek, 27 May).
When he secured the post, he says he assured his wife it would not be possible to work more hours than he already did, but the lack of sleep appears to be taking its toll.
Reminded that Margaret Thatcher claimed to function on four hours' sleep a night, Smith is quick to insist he is not associated with 'that woman'.
He explains his lack of sleep is partly due to kicking a 20-year smoking habit.
As he perches on his chair in the West End office, he declares quite matter-of-factly: 'My doctor has told me I won't get through my sixties.'
Now 41 and at the helm of the agency's 110-strong operation, Smith pledges to shake up the agency by cutting red tape, changing the culture and expanding all areas of the business. He identifies technology, healthcare and public affairs as practices earmarked for particular growth.
On Edelman being a privately run family business, he says: 'The advantage is that the people who run it are close to the customer. We do not need to squeeze our margins to please someone in the US.'
Science was a major part of Smith's past. Having attended Tunbridge Wells Grammar, he studied science A-levels - 'because that's what boys studied then' - before joining Kent University. A place at Oxford followed, where he undertook a PhD in chemistry and environmental science.
He spent his Oxford days examining the diminishing ozone layer with fellow student Douglas Parr, now Greenpeace's chief scientist. But unlike many of his course buddies, Smith never joined peace or environmental activist groups and strongly refuses to be described as a 'greenie': 'I was interested in the science, finding the truth - not the policy.'
As a student he worked behind the bar at the famous Lamb and Flag pub, rowed for his alma mater and played hockey for Morris Motors. Slightly built, it is hard to imagine Smith taking part in these demanding pursuits, but despite his calm persona, there is another side to the man who describes himself as 'bold', 'driven' and 'unafraid to make difficult decisions'.
Smith stops short of the adjective 'ruthless', a label used by one former colleague.
After Oxford, Smith joined scientific consultancy CES, before taking up his first PR role at Burson-Marsteller as an associate director in 1989. His next steps took him to 3M as corporate marketing and comms manager for the UK and Ireland. He was then head of comms at the Audit Commission, where he was charged with the introduction of 'best value audits', a milestone in the organisation's history.
Smith joined Edelman in 2000 as a director in its corporate and public affairs practice. He was appointed joint London CEO in 2003. 'I can't see myself ever working for another agency. There is so much freedom here,' he enthuses. 'I want to leave a cultural legacy.'
On the subject of this potential legacy, Smith pledges to improve training and internal communications; he says he wants to consult everyone in the agency, to encourage them to buy in to its business plan.
Smith will be occupied with this mission for the next two years, after which he fancies a spell in Asia - possibly with Edelman.
In the meantime, Smith's staff had better brace themselves for long hours in front of those flipcharts.
1988: Consultant, CES
1989: Associate director, Burson-Marsteller
1993: Corporate marketing and comms manager (UK and Ireland), 3M
1997: Head of communications, Audit Commission
1999: Director, Edelman
2005: CEO, Edelman London