The Commons Select Committee's investigation into Britons' ever-expanding waistlines has, literally, put the fat in the fire.
Press coverage has stoked the emotional flames, not least in the reporting of the death of a three-year-old girl weighing six stone. "Child, 3, dies of obesity," The Sun's splash screamed.
No matter that the story proved false and that the girl's death was the result not of obesity but a rare genetic abnormality. Lurid stories of children "choking on their own fat" are hard to dispel.
It is Preston's unenviable task to make the case for beleaguered food advertisers and their agencies. He must strip the hysteria out of the debate and stimulate more cool and dispassionate argument.
For the FAU's advertiser members, in particular, it's a job for which he is admirably suited. The former managing director of Cereal Partners UK has spent his entire professional life in the food industry with companies including Wall's Meat, Macfisheries and Unilever. He was the sales director of RHM for seven years.
Malcolm Earnshaw, the ISBA director-general, marks Preston out as "a very capable, experienced and committed operator who is doing an excellent job". Other advocates describe him as a driven and determined man, who has not only brought sound professional and financial management to the FAU but has the kind of business and social background - he's a passionate cricket lover and golfer - capable of getting the FAU's voice heard in influential places.
"He has immense charm and good sense," Hugh Burkitt, the Marketing Society's chief executive, says. "You feel that he genuinely understands the problem."
Hamish Pringle, the IPA director-general, agrees. "He's brought a large amount of energy and commitment to the role," he observes. "He's a powerful speaker, good at taking into account the political sensitivities and nuances."
Others though, mainly in the agency community, express disquiet about what they see as a legacy of his previous incarnation. "When he deals with agencies, he still behaves like a big swinging dick client when he should be energising people and getting consensus," an insider complains.
"He's a bit too strident for my taste," a senior agency manager says. "He always wants to be in control and expects you to stand to attention and salute the flag without question."
Indeed, Preston is known to have been less than pleased about a story leaked to Campaign that the FAU was talking to Abbott Mead Vickers BBDO about a possible food industry-funded campaign to promote healthy living.
Moreover, his decision to approach AMV has irked some other FAU member agencies, which believe he should have opted for a collaborative approach.
Preston acknowledges his natural instinct to put the screws on agencies.
"If it's a criticism, then I suppose it's a fair one," he admits. "But when you've been a client for 40 years, as I have, it's very hard to change your habits."
Nobody in the industry doubts the scale of Preston's challenge. The Select Committee has effectively put food advertisers on a yellow card and will urge the Government to act if the industry fails to put its house in order.
The heat was turned up even further last week when the British Medical Association agreed to press ministers for a ban on the advertising of unhealthy food before the 9pm watershed.
Preston takes this in his stride, arguing that interventionalism isn't the answer. Doctors are busy people who "may not necessarily have been so closely involved with the issue as we are", he says.
Some believe Preston's situation isn't helped by the status of the FAU, a not-always-easy alliance between food advertisers, agencies with significant food business and media owners. Although operating under the AA's wing and with access to its resources, the FAU is semi-autonomous and can seek funds directly from its stakeholders.
The unit was established in 1995 by Lionel Stanbrook, then the AA's deputy director-general. At the time, co-operation between consumer groups across Europe was building. The intelligence Stanbrook was receiving from those groups convinced him food advertising to children was going to become a major issue and that there was a need for a dedicated and properly resourced operation to make the industry's case.
Despite winning an undertaking from ISBA that the FAU would handle the highly contentious issue of advertising to children, funding remained problematic. Some companies questioned why they should be bankrolling the FAU when they were already contributing to their respective trade organisations.
With resources stretched, the FAU's impact was limited. Although Stanbrook returned briefly to get it back on course after quitting in 2000, he and Andrew Brown, the AA's director-general, agreed the FAU was in need of a strong leader who could extend its influence.
Preston's recruitment was seen as a significant coup. He introduced the kind of business discipline the FAU hadn't previously seen. "This approach doesn't always go down well within the hallowed portals of the AA," a former senior executive admits. "But Brown is flexible and pragmatic and is keen to back things that work."
Preston won't discuss the FAU's funding but it is understood member agencies' annual contributions - up to £10,000 - are based on the size of their food business.
Nevertheless, industry sources claim this has resulted in internal tensions, sparking fears that the tripartite system, on which the FAU's credibility is based, could be put at risk with the FAU becoming no more than a mouthpiece for advertisers unless it's very careful.
Some advertiser members already complain that agencies should be paying more. Meanwhile, Preston has been keeping the pressure on adland, warning that it will be the big loser if the Government chooses to legislate.
"He has been hard-selling this to agencies but some are finding it a bit strong," an industry executive says.
Preston's appeal has also been undermined by what some agencies believe to have been the Food and Drink Federation's poor performance in the PR battle since the Select Committee's report was published. "It's astonishing that the federation, having known several weeks in advance what the committee's probable verdict would be, didn't retaliate in advance," a trade body source says. "And why wasn't it the food industry that nailed the lie about the death of the overweight child?"
Preston believes this is easier said than done. Scare stories are appearing every day, he points out, and it's hard for the case to be made when so many national newspapers have a pre-ordained agenda and the industry's response is restricted to a couple of lines at the end of an article.
While no-one blames Preston for the situation, agencies believe the FAU should be pushing the federation to be more pro-active on the PR front.
"Jeremy's a fine figurehead but he needs a good PR operation alongside him and, maybe, some agency planning expertise as well," Burkitt suggests. "It's hardly a huge investment when set against what's at stake if he fails."
Family: Married with two sons
Favourite ad: British Airways "face"
Describe yourself in three words: I hate losing
Greatest extravagance: My wife
Most treasured possession: Set of Wisden cricket almanacs
Most admired agency: I couldn't possibly comment
Living person you most admire: Lance Armstrong (US cyclist)
One to watch: China
Motto: Tell me and I'll forget, show me and I'll remember, inspire me
and I'll respond