LONDON — Vineyard vocalist Katie Mayhew made her international debut at London’s Cadogan Hall, singing her signature Sondheim song Being Alive, which won her the 2008 Boston Pops high school sing-off and the notice of the British director who staged Wednesday night’s Inspiration Awards for Women ceremony.

The 2010 Martha’s Vineyard Regional High School graduate was described as “the new singing sensation Katie Mayhew” in the press release for the awards, which honored 11 women, including actors Emma Thompson and Sandra Bullock and celebrity chef Nigella Lawson, who have in some way inspired or been role models for others.

A movie screen above the stage projected live images of Ms. Mayhew performing in a diaphanous white gown. Phenomenal acoustics in the huge, hangar-shaped hall, home of the Royal Philharmonic Orchestra, intensified her sound.

As Ms. Mayhew closed out the first act of the evening, which included several musical interludes, the astonished emcee quipped, “You won’t see that on American Idol!”

His tone was obviously critical of the TV show. But she was radiant and looked delighted. Backstage, the show’s choir took a minute of silence in honor of Katie’s performance.

“It was great,” was her only initial comment after the show. When prodded for more, she admitted she had been nervous. “I was trembling. It was the heels. Seriously, I wouldn’t have been trembling if I wasn’t in heels.”

The event was part of the already rich story of a young performer. Most Vineyarders know Katie from her Boston Pops performances, or her roles in many Island musicals, including the high school’s spring production of Rent (as Mimi) or this summer’s Island Theatre Workshop’s production of Putnam County Spelling Bee (as TK).

It was also part of the story of her family, especially her mother, Deborah, who gracefully manages the tricky balancing act of promoting Katie without pushing her, encouraging her without entitling her. Deb is not a stage mother; she is a team member. Other family members help make up the team, including Uncle Jack (recording engineer), Auntie Sarah (photographer), and Deborah’s partner Todd Follansbee (all-round unsung hero).

But this was also the story of English theatre director Michael Strassen, and therefore a story of fate, or serendipity, or karma — or as Darwin fans Michael and Katie might prefer, utter randomness.

Mr. Strassen (“Strass,” as he is called by his friends) grew up in a working-class family in the north of England, where he was “embarrassed into” joining a neighbor’s drama group at age 16. He had an aptitude for performing. For his 18th birthday, his mother told him, “You can either have a big party, or you can go down to London to audition for drama school.” He chose the latter, and got into Guildhall, an acclaimed acting conservatory. His first job after graduating was a national tour of Annie in which he understudied 11 different roles. Over the years he developed an impressive resume, mostly of musical theatre roles, including a turn as Marius in the West End production of Les Misérables.

Eventually, Mr. Strassen turned to directing and developed a particular passion for Stephen Sondheim’s work. He recently directed a production of Assassins (controversial because he re-interpreted one of the characters as a Barack Obama-type figure).

Earlier this year, he agreed to direct Inspiration Awards for Women. It’s a wonderful cause — ticket revenues for the event go to Breakthrough Breast Cancer, Britain’s largest nonprofit dedicated to eradicating the disease — that draws a lot of media and celebrity attention, so Mr. Strassen was happy to take the gig, especially as he would be free to intersperse musical numbers into the evening.

But ironically, he was having a hard time getting inspired about the Inspiration Awards. “I believe in their importance, but cancer as an issue is so general, it was hard for me to develop a personal hook into the project,” he explains.

Meanwhile, while randomly surfing YouTube looking at performances of Sondheim songs, he discovered a video of a teenager from America named Katie Mayhew, singing Being Alive for the Boston Pops.

“Within four bars, I knew she had what it takes,” he said. “And that was it. I had my inspiration: I was going to bring Katie Mayhew to London and be the one who discovered her.”

He left a simple comment with the YouTube video: “World class voice — Michael Strassen.” Deborah Googled his name, discovered who he was, and got in touch with him.

“I responded because it was Katie’s mother,” he said. “If it had been Katie herself, I would not have; it would have been dicey for a teenage girl to befriend a strange man over the Internet.”

Over the course of five months, Mr. Strassen and the Mayhew family developed a lively online friendship, and the director became determined to bring Katie to the awards. He ran this by the show’s producer, Sky Andrews. The initial answer was no; why pay to bring an unknown teenager all the way from America when London is full of established top-notch vocalists? Mr. Strassen argued with him: “But the best singers are all performing in West End musicals that night.”

Grudgingly, Mr. Andrews agreed to watch the video of Katie performing. “Get her over here,” he said as soon as he’d seen it.

So Katie and her family (and myself) went to London. The production put them up in the swanky Mayfair hotel. They had a couple of days to acclimatize and see the city — though their bus tour was hampered by traffic created by a subway strike, and Katie’s mother tried to distract everyone from the terrorist alerts that screamed from newspaper headlines.

After months of e-mails, Facebooking and phone calls, Team Katie finally met up with Mr. Strassen in person the night before the ceremony took place.

We were to meet up at 6 p.m. at Picadilly Circus by the famous statue of Eros, the place where hundreds of people, many of them tourists, were meeting up. Yet when Mr. Strassen appeared from the crowd, he and the Mayhews recognized each other at once; Katie went forward to greet him and they hugged ebulliently, then he likewise hugged the rest of the group.

“It was great to meet them in person,” he said later. “They were all so lovely over the Internet but in real life, you [never] know.”

Mr. Strassen took the group to The Lord Salsbury, probably the most ornate pub in London. Over drinks (Katie is legal in the U.K.), the group talked animatedly about everything from theatre to Darwin. For dinner Mr. Strassen wanted to choose someplace “where we could be loud and generally excitable;” at a small eatery called The Stock Pot, the conversation was lively again, this time with an emphasis on Katie’s career. There was a technical discussion of vocal technique, and praises were sung to Linda Berg, the Vineyarder who was Katie’s voice coach from the age of eight until she went off to college this fall.

Later came a walking tour through Soho and Chinatown, ending eventually at Jewel, a very eclectic nightclub, for yet more lively conversation, ranging from Bernadette Peters to EST. When the evening wrapped, it was just 12 hours before young Ms. Mayhew was expected at rehearsal.

She arrived there to find people in black rushing around, tending to technical matters as the seven-piece band warmed up. For sound-check Katie was dressed not unlike Mimi, her character in Rent; she sang a cappella, then several times with the band, as a blue spotlight lit her from the front and a toplight of random changing colors glowed on her from above.

Mr. Strassen walked her through her entrance, issuing instructions to both performer and lighting designer on the effect he wanted. He worked with Katie and the band for half an hour on certain specific moments in the song, which they practiced over and over again.

“She’s gotten more instruction on this song from him than everyone else put together,” says Mr. Follansbee admiringly.

Somebody watching heard that Katie is majoring in biology and declared, incredulously, “She wants to be a doctor?”

After rehearsal, it was back to the Mayfair to rest.

But by 6:30, she was back at Cadogan Hall, in a dressing room, in gown and makeup. Mr. Strassen appeared to give her some notes about how to curtsey, accept the applause (“Give them the full Bernadette arm, and then come back to yourself: oh my God, I’m embarrassed by my own talent”) and exit the stage.

Random well-dressed people with a variety of UK accents wander the underground halls preparing for the event. Most are famous to Britons; we have never heard of any of them. Outside, dozens of photographers (including Sarah Mayhew) have assembled along the pink carpet, waiting their chance to take photos.

At 7, Katie, like everyone else involved in the show, left the hall by the stage door, walked a few yards down the sidewalk, and then prepared to re-enter the building along the pink carpet, before the cameras. Mr. Strassen made sure the photographers and journalists knew who she was, then he took Katie by the hand and escorted her onto the carpet; after about 10 seconds, he left her to face the classic paparazzi strobe-light effect on her own.

Voices shouted out: “Turn this way! Show us your profile! Your face this way, please!” Katie handled it all with remarkable calm and naturalness. Then she entered the lobby of the hall, which was literally stuffed with people. The temperature was 15 degrees warmer there; the clamor of voices was deafening; it was impossible to move without brushing, and sometimes rubbing, against other people. After another round of photography against a “Breakthrough Breast Cancer” backdrop, Katie went downstairs to wait for her cue.

When she appeared on stage, about an hour into the show, it was delightful to watch how she took all of Michael’s directions from earlier in the day. Simply put, she is gorgeous and brilliant.

“Nice curtsey,” Mr. Strasses said to her afterward. “You’ll need to practice that for when you meet the Queen in 10 years.”

He already has informed her that once she graduates from college, he wants to bring her back to London to be in a show he’ll direct.

This is just the overture.