"The people there were charming, and I seemed to satisfy all the criteria - kind, caring, and so on - but within a few minutes I was out on my ear." The one criterion he didn't fulfil was that of his sexuality: he wasn't gay.
"They were banging a particular drum, and it wasn't a tune I was marching along to." But they did refer him to another outfit, in California, where, though as a straight single male he remained a distinct minority, he was promptly signed up.
Then began the process of finding first the surrogate mother (the provider of eggs) and next a birth mother (the womb).
It was important, Mucklejohn stresses, that he found women who were offering themselves for the right reasons. "And I did. Both were absolutely lovely. They told me they had led ordinary lives, but that this gave them the opportunity to do something special."
Whenever he recounts the story now, what people most want to learn, he says, is how much it all cost him.
"I plucked a figure out of the air for the press, I think it was £50,000 ($97,000), but in truth I don't think it was even that much. Basically, you recompense the surrogates for lost earnings, so in my case it was a nurse's salary for a year, and medical insurance to cover hospital costs."
In 2003, four eggs were harvested, then implanted. Three took: triplets. Scans suggested to doctors he was having girls. Instead, several months on, out came boy after boy after boy.
Mucklejohn, 65, inexplicably for a single father of three, looks a good decade younger and his boys, Lars, Piers and Ian, are 11. He has written a book about their lives together, A Dad for All Seasons: How My Sons Raised Me. The proceeds of the book will go to charity.
This is his second book. Seven years ago, he wrote And Then There Were Three: Diary of a Truly Single Father, prompted into doing so when his story reached the press and unleashed, in certain circles, a somewhat hysterical reaction.
The Daily Mail wrote critically about what he'd done, and when he appeared on a television talk show, a fellow guest, a religious affairs correspondent, insisted that he had created three disabled children.
"She said they would always lack the cut and thrust that exists between a mother and father, and that they would never experience a parental argument," he says.
"Personally speaking, I think children need parental arguments like they need a hole in the head."
Reactions in his hometown of Newbury, however, were more restrained, more level-headed, and he was quickly accepted by all as just another single parent - hardly an oddity. He had brought his boys home from the US when they were 6 weeks old, and because he had read that, should the authorities ever investigate, they would look to find "a female presence at all times", he employed a maternity nurse for the first month to help with the feeding, and then, for the next year and a half, nannies: one for weekdays, one for weekends.
"But the authorities never did come calling, and by the time it came to potty training, I wanted to raise them by myself," he says. "It's been the four of us ever since."
Mucklejohn runs his own English language school for foreign children, and regulates his working hours around school and after-school activities. "It's hectic," he admits, "and I don't sleep very much, but I'm not complaining."
But then, he reasons, life is a series of functions in which he never puts himself first. "I suppose I've always been responsible for other people, both privately and professionally. Being a carer to someone with brain damage often means you are thankful when things don't get any worse, but they rarely get better. A baby doesn't throw a nappy at you with the intent of causing damage, does it? That was my situation in my caring role. Parenting is much better, and much more fun."
Although his unusual situation did bring him plenty of female attention initially, he insists he is simply too busy to have a relationship, too devoted to his sons. And so he remains single at his now pensionable age.
"I actually believe that age is an advantage in parenthood. A lot of younger parents are still working out who they are, but I've experienced things, I've done things, and considered them, reflected on them. So I hope what I introduce to my boys' lives is some rationality, and perhaps a little wisdom."
- Independent