For her 18th birthday, in 1981, Carol Marsh's parents gave her a ZX81 computer. The ZX81, a small black box with four chips, a single kilobyte of memory and a tendency to overheat, was the first mass-market computer, and got a generation hooked on messing around with circuit boards.
"You could buy it as a kit. It came with instructions so I put it together. I never thought anything of it," she says.
Marsh went on to become one of the first women to gain a higher national diploma in electrical and electronic engineering at Napier University, in her home city of Edinburgh. The first in her family to go to university, she fell into the world of logic gates and binary numbers, discovering "the thrill of designing things and seeing them work".
When she got married in her third year, her tutors assumed she would leave the course. "Not only did I stay, but I got a distinction," she says, matter-of-factly.
Three decades on, Marsh has a doctorate in engineering and a senior job at Selex ES, the international defence engineering firm, where she oversees the design of digital chips used in radar and lasers in commercial and fighter jets.
Although not as scarce as a ZX81 is these days, Carol Marsh is still in a very select group. Only 8% of British engineers are women, the lowest proportion in Europe, and well behind Germany (15%), Sweden (25%) and top-performing Latvia (30%). A growing number of companies are saying this is a problem not only for them, but for all of UK manufacturing.
The manufacturers' organisation EEF reports that four in five firms are struggling to fill their vacancies. "That is because the talent pool is pretty much half of what it could be," the EEF's Verity O'Keefe says. "If we are not really tackling that [gender] issue, we are going to have larger skills gaps than other industries that have done something about it, such as medicine."
Dave Dalton, chief executive of the British Glass Association, says UK manufacturers could lose their competitive edge, as the battle for brainpower intensifies. "I know the future is not going to be about physical endeavour; it's going to be about mental endeavour, and 50% of the population are female. Why are we not attracting that potential?"
The problem starts long before people pick a career. Too many youngsters are ditching maths and science as soon as they can, a trend especially marked for girls. Almost half of mixed state schools in England failed to enter a single girl for A-level physics. And when it comes to careers most valued by parents, engineering is right at the top - for boys. But teaching and nursing come top of parents' wish-lists for their daughters.
Elena Rodriguez Falcon, a professor of enterprise education at the University of Sheffield, thinks the problem starts in the nursery. "Children's books are filled with social constructs: the girl is a nurse; the boy is a firefighter." Another storybook fable she wants to demolish is that "engineering is a dirty, badly paid profession". Many people misunderstand what engineering is about, she says. They associate it with car mechanics, rather than well-paid graduates designing ultrasound scanners or smartphones.
Engineering and manufacturing firms have to compete with medical schools for the tiny pool of women who have done maths and science A-levels.
Katrina Love, 18, from Sheffield is studying A-levels including maths and chemistry: she is just the kind of bright student they hope to attract. She had looked at doing medicine and dentistry, but says recent open days have opened her eyes to mechanical engineering. Her younger sister Sarah, 16, is thinking about an apprenticeship, but has run into scepticism: "[People] start to question why you are doing that - why you don't do a more feminine role, like nursing."
Julie Watson, 50, says she has seen little sexism in her 30-year career at a bottle plant in Knottingley, West Yorkshire. When she took a summer job at the plant aged 17, in 1983, she was set on a career in fashion, but discovered that "glassmaking was in my veins". By age 25 she was a supervisor, overseeing bottle production, at a time when most women at the plant were assembling cardboard boxes.
The "gender thing" came up only once: when an all-male panel was considering her application for a five-year training course in glass technology and engineering. "They asked: 'Why do you want to apply for something like this? Wouldn't you be more suited to a secretarial position?' I found myself convincing them that I could actually spray-paint my own car."
Today she's operations director, overseeing 260 employees. She likes to invite schoolchildren into the plant, to show them how piles of grey sand are transformed into clinking bottles.
O'Keefe thinks such female role models will be a big help in closing the gender gap. A decisive factor in girls' take-up of apprenticeships is whether a "key influencer" showed them what was possible, she says.
However, it is not just attracting women into the workforce that is crucial, but keeping them. In a report last year, John Perkins, chief scientific adviser to the business department, called on employers to spend more on helping women return to work after a career break. At Selex ES, Marsh says employers should do more to help women - and men - resume careers after time out: "Engineering is difficult to come back to because it changes so quickly. You have to retrain, and you can lose confidence."
But can these measures make a difference before manufacturing, now reduced to just 10% of the UK economy, shrinks even further?
Rodriguez Falcon sees a link between female participation and a strong manufacturing base. "When you are surrounded by engineering, you can very clearly see what it is and what it can do in your life," she says. "Unfortunately, in the UK, industry is disappearing, slowly but surely."
The national shortage of engineers is "a serious threat to the recovery", according to Vince Cable, the business secretary. Cable said he was especially concerned at the lack of women in the industry: "Within the overall problem of the shortage of engineers we have extreme under-representation of women."
The Liberal Democrat said he was encouraged by greater awareness of the issue, but that the problem went back to the choices made at secondary school: "Now that we are getting more into a recovery mode, companies are naturally concerned about what holds back expansion. And lack of skilled labour is emerging as number one."
Cable said the UK had "probably over-deindustrialised", leaving manufacturing accounting for just a tenth of the economy. "To have a rebalanced economy, we should have preferably a higher share of manufacturing - but you can't just create it out of thin air," he said.
Batting away criticisms that the coalition had abandoned "the march of the makers" in favour of a consumption-fuelled boom, he said: "The government now understands the rebalancing strategy. It is reversing decades of fatalism about [manufacturing] contraction and seeing this as area of potentially significant expansion."
Julie Watson had to argue her way on to an engineering training course. Photograph by Christopher Thomond for the Observer