Gregor, just 29, will take up his new role next week after a holiday with his partner in Lanzarote.
His title as the MHRA's first comms director is no coincidence as pressure intensifies for increased transparency of pharmaceutical research findings - and as the Health Select Committee continues its inquiry into the drugs industry's 'influence'.
The appointment of Gregor, a bookish hiking enthusiast who describes himself as 'energetic' with a love of 'being with people', is one of the early fruits of a comms audit last year by consultancy Stonehenge PR.
'One of the findings of the review was that the interaction of the agency and its predecessors (with the media) had not been as good as it could be,' he explains.
The MHRA's media relations function is currently run by the Department of Health, but Gregor is to set up its own PR unit.
But the part-public, part-Big Pharma-funded body's handling of information on anti-depressant Seroxat's potential side-effects in particular has led to criticism that it is too close to industry and government.
Does Gregor think the body itself, not just its PR, needs an overhaul?
No, he says, arguing the agency needs to communicate more proactively: 'So instead of just publishing information, (proactive communication involves) seeking to engage people and saying "here is the information, let's have a discussion about it, let's try to make sure people understand these issues".'
Genuinely enthused, he suggests that the way to achieve this is to generate 'dialogue' between the public and scientists on drugs' benefits and risks.
The day before his PRWeek interview, Gregor watched MHRA executives give evidence to the Health Select Committee.
Asked how the session went, Gregor says: '(MHRA chairman professor Sir Alasdair Breckenridge) raised the point right upfront about this need for a debate about risk and benefit. We need to start having that debate much more openly and engage the public and the media. I felt that position was clearly set out.'
So how did a graduate with a 2:1 in English from Fitzwilliam College, Cambridge, end up as a high-flying PRO in the healthcare sector? PR, he says, interested him most in his first job, working in the national sales and marketing department at accountancy firm Grant Thornton.
But besides having family in the medical profession - his mother is a retired medical secretary and his father works for Care in the Community - what attracted him to public health, was an interest in 'science in action' and a desire to 'make a clear link' between his career and individuals' lives (he wrinkles his nose at how 'terribly worthy' this sounds).
This drove him forward through roles of increasing responsibility, first at Hampstead's Royal Free Hospital, then the 'germ police' (protecting the public against disease outbreaks at the Public Health Laboratory Service), before his current role.
Stonehenge PR co-founder Geoff Potter, a former GSK corporate communications senior V-P, lauds Gregor's 'maturity of judgement' for one so young. National Patient Safety Agency comms director Jenny Grey agrees. 'The MHRA faces a massive challenge post-Seroxat to grow its credibility among stakeholders,' she says. 'But Simon should do very well in handling this challenge at a body that (previously) had no real grown-up, strategic, co-ordinated communications.'
This week's 'doing nothing' holiday in Lanzarote may be Gregor's last opportunity to do just that for some time to come.
1996: Marketing and PR assistant, Grant Thornton
1997: Press office assistant, Royal Free Hampstead NHS Trust
1998: Press officer, Public Health Laboratory Service
1999: Head of press and media activities, PHLS
2001: Head of external comms, PHLS
2003: Director of communications and external relations, National
Clinical Assessment Authority
2005: Director of communications, Medicines and Healthcare products