On my first visit to Turnbull & Asser’s flagship Jermyn Street shop in London, I purposefully wore a Thomas Pink shirt, thinking that I was being quite smart. The collar of this shirt is a roomy 16 inches, the left sleeve comes far over my wrist while the right sleeve refuses to come near my wrist, and the shoulders tend to scrunch up to the left. None of this struck me as a problem until I met Andrew Courtney, who has worked with Turnbull & Asser for 10 years and who was wearing a perfect bespoke shirt. Suddenly my smartest, most expensive shirt felt like a shameful smock.

Mr. Courtney was far too polite to point out my sartorial failings. Rather, he immediately set me on the right course, loading me down with several books of fabrics, many of them exclusive to Turnbull & Asser and all of them designed in-house. A series of angst-ridden choices followed, as photographs of Turnbull & Asser customers through the ages stared down at me. There was Ronald Reagan, who was recently buried in a Turnbull & Asser shirt, several incarnations of James Bond, the Prince of Wales, Liberace, and Picasso. But Turnbull & Asser is the type of firm that is name-dropped by its celebrated clients, rather than the other way around.

As my Pink number bunched up further around my waist and billowed out in an increasingly unacceptable manner, I settled on a blue shirt with two raised medium blue panels set against red and black lines in two-fold Egyptian cotton. More choices followed, and I was led by Mr. Courtney to choose the standard, often imitated, Turnbull three-button cuff over French cuffs or the Turnbull innovation, the cocktail cuff. I also chose the Prince of Wales collar and, again on advice, opted not to have a shirt pocket.

Then came a series of 13 measurements, in addition to a consideration of stance and shoulder positions. I learned a few lessons: For instance, the measurement across the chest always matches one’s neck size and the foot size matches the distance from your elbow to your hand. My watch was measured, which struck me as extremely sensible. And I was told that one of my arms is slightly longer than the other.

I expected to balk at the cost of Turnbull shirts but was surprised to hear that, though the minimum order is six shirts, the cost for each can be as low as $200, the same price, more or less, as my Pink number.

Usually it takes three weeks for the sample shirt to be made up. The customer then washes and wears it, rather like approving a glass of wine, and following his approval the remainder of the shirts are made up in eight weeks. At the moment, though, given a backlog of orders, the completion time for shirt orders is about 14 weeks.

The brown envelope with my measuring details was then transported to the Turnbull factory in Gloucester. I followed this envelope down to Gloucester with Helena Mountford, the chief executive officer of Turnbull, an energetic young woman who seemed particularly patriotic, pointing out that the shirts are entirely made in Britain, an increasing rarity in fashion and menswear in particular.

The factory is a bright, airy, and efficiently busy modern building on the outskirts of Gloucester. Until last year, production was done at two older factories in the area, and productivity has increased dramatically since the operation was moved to the new, custom-designed location. The place was a dizzying beehive of activity, so I started in the tearoom and surveyed the factory floor. The operation there begins in a clockwise fashion against a wall holding dozens of bales of material.

I met the pattern maker, Michael Jeffries, introduced as the technical guru of the factory. His job is to get the patterns of the shirt onto the computer and then make changes to them with an electronic tracing board. Already he knew more about me than anyone who has never seen me without a shirt on – he marked a drop in my left shoulder, along with a few other details that do not need mentioning in a public forum.

Mr. Jeffries mentioned that “seven years ago, the most technological kit we had was a calculator.” Given that the company has been making shirts since 1885, this gives one pause. Other than the computer, the tools of the trade seem to be shears, sewing machines, and dozens of pairs of accomplished craftsmen’s hands. As Mr. Jeffries put it, “Now we have the best of both worlds – using modern technology and craftsmanship to be as precise as possible.”

Twenty-five separate pieces of cloth and a further five pieces of lining were laid out to make my shirt, including two distinct sleeves, rather than the usual practice of having two sleeves and then cutting one of them down.

This mound of material then moved along to Peter Matthews, the cutter and supervisor, an imposing gentleman who took an even more imposing set of shears and cut some of the fabric with impossible delicacy to make the cuffs. Then, wearing some medieval chain metal gloves, he took some material to the bander machine where a quarter of an inch was cut off.

I proceeded to the liveliest area of the factory, where a group of four women were surrounded by 10-year-old sewing machines. Madonna was playing on the stereo, which seemed fitting as this group is referred to as “the material girls.” Even more fitting was the fact that my shirt was holding up their next job, some shirts for Sean Penn.

These women spend 80 to 100 minutes working on one shirt and their goal is to produce 87 shirts a week. As I observed such minute details as matching up the lines of the fabric on each cuff, I said that I had no idea so much work went into what is, after all, just a shirt. “All this effort, and they have no idea how hard we work,” one of them replied.

About 100 minutes later, the 30 pieces of material had taken form as a shirt and were moved along to have the mother-of-pearl buttons sewn on properly. The label was also affixed at this time.

The last stage was with a woman named Jean, who told me that for the VIP customers, everything has got to be perfect. “Who’s a VIP?” I asked. “Well, everyone, really,” she said. At that moment, she was putting the finishing touches on 10 shirts for Sir Tim Rice. She snipped out bits of thread and put bones into the collar. Then the shirt was placed on a body press machine; the board sucked the shirt material in and pressed it with a rather dramatic, finite flourish. And there the story ends – three pieces of tissue folded into the shirt, no cardboard or pins, just a perfect finished shirt.

A few days later, I went by the Jermyn Street shop again to pick up the finished product. This time I was wearing a Gieves and Hawkes shirt that had previously been one of my more prized possessions. Now it felt like an unconvincing blouse.

I tried on my new shirt and had a sensation far more immediate and intimate than the moment when I tried on my first tailor-made suit. Suddenly my torso made more sense, as if I had finally undergone that three-month exercise routine I keep meaning to undertake. Even before its first washing, the shirt accentuated the positive while discreetly tucking away the less than perfect bits. I didn’t look any more spectacular than usual, but after years of looking like myself gussied up with Helmut Lang or Paul Smith, I just looked, and more importantly felt, like myself.