Tall and broad, it is hard to imagine he is ruffled when making home visits in Clydebank.
Equally, as the new chairman of the British Medical Association's Scottish GPs Committee he must walk into rooms ready for difficult discussions with NHS executives feeling equally at home.
This is someone who can wear a Winnie the Pooh tie with a short-sleeved shirt and still appear calm and in control, even though he misses a flight while we are talking.
Perhaps this is because he is used to the intense pressure of looking after patients, dealing safely and sympathetically with their medication, their bad habits, their latest test results and the problems they want to talk about, all in the space of 10 minutes.
But while he might not sound stressed, he is very clear that GPs cannot be asked to do any more work, be it delivering public health messages on obesity, for example, or turning round extra blood tests for hospitals.
"Although there is a lot more we could do, we are not going to be able to do more now," he says, straight-forward as ever. "We are at saturation point, and have been for some time."
He has many examples of how a GP's day has been increasingly consumed, and a number involve the care of patients who have been discharged from hospital.
"Every day a practice will be asked, do you mind doing this extra follow-up, this extra blood test?" he says.
In the past, hospitals wrote back to GPs saying patients had been treated, he explains, now they come back asking GPs "to do things for patients which they have forgotten to do".
I can, actually, imagine him on the phone in his surgery trying to contact a consultant to check whether a change in a pensioner's medication during her recent spell on the wards was deliberate or accidental and feeling a little warm under the collar as the phone trips to voicemail and he wonders when he will be able to call again, given the waiting room is full.
This is because, although he describes GPs taking on many jobs which were once performed in hospitals, he says the relationship between primary and secondary care has never been more distant.
"We have lost contact with clinicians in secondary care," he explains. "Even things like joint educational meetings are less frequent. We do not meet them."
Once, not that long ago, GPs referred patients to individual consultants. Today, Dr McDevitt says, they refer to a hospital service and the patient will be sent to "wherever the shortest waiting list is - If something happens to that patient in the meantime, I cannot speak to an individual clinician."
In fact, even talking to their secretary has become complicated. Consultants are losing their secretaries and now share pools of administration workers and "IT solutions", he says. The move to remote call handling switchboards instead of hospital receptions – where those who answered the phones knew the staff, has also sparked complaints.
I ask him if it matters, this breakdown in multiple lines of communication.
He says: "It matters hugely because it is not good for patients. Quite often there are mis-understandings on how things should happen. It is one of the big things that needs to be addressed in the NHS, to bring things together."
In the worst case scenario, he tells me, patients end up being readmitted to hospital.
He says: "It is expensive to have people in hospital and it is traumatic for them. We want them to be sorted when they come back out. Sometimes, if it is not well organised the person can end up going back to hospital unnecessarily because it was not well planned.
"I am sure there are elements in general practice where we should improve what we are doing and we should be sitting down and saying how can we make this work?"
He knows that, particularly in the current financial climate, health boards have no choice but to become more efficient – and the massive drop in waiting times has been very good news for patients. He just feels clinicians could be more involved in the way these changes are managed because "sometimes people do not realise what the impacts will be".
The strategy being pursued by the Scottish Government to shift care of the elderly and the terminally ill out of hospitals into their own homes will require more GPs, he says. Doctors need to be involved in the planning of the major changes already under way, for example moving responsibility for adult community care from councils to health boards. Dr McDevitt, 49, says: "Sadly we have already had reorganisations where doctors have had no effective voice in the process and sadly doctors have stepped back because they felt that, and I think the service has suffered as a result."
For at least the next three years he will be the voice for GPs in Scotland and while this will take him away from his surgery some of the time, he still believes the aim is the same: looking after patients.
"My mother always said you do not have to wonder why you are getting up in the morning if you are a doctor because you know you are going to help people," he tells me.
It was his mother's doctor who inadvertently encouraged Dr McDevitt to enter the medical profession. He remembers her coming home from the surgery, much reassured, after being told: "You are just wabbit, you have five children under five."
Dr McDevitt, who grew up in West Lothian, says: "I was always impressed that the doctor understood there was nothing physically wrong and he always reassured her."
His aim for his time as chairman is to increase the capacity of general practice, to ensure there will be more doctors, staff and space to take on additional work in future.
Reason enough, his mother would hopefully agree, for climbing out from under the covers each morning.
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