"I knew something was wrong but, when I got up the courage to talk to a teacher, she told me, 'Everyone enjoys a drink' and that I shouldn't worry." John died two years ago, after a catastrophic decline, but the damage caused by his drinking is still taking effect.
Today, Jenny is back at home in Blunham, near Bedford, her life at an abrupt standstill after six years of working in London as a marketing manager.
"A few months after he died, I had a breakdown," she says. "It's as if, after all those years of stress, you suddenly stop and everything that has happened floods over you. I needed a complete break to re-evaluate my life."
Jenny is far from alone in having her life shattered by someone else's drinking.
We tend to regard a problem drinker's 'few too many' as only harming themselves but new research shows that is simply not true. Totting up the myriad ways in which people are damaged by so-called 'secondhand' drinking, the California-based Alcohol Research Group estimates that an extraordinary one in five adults is harmed every year. The ARG paper says "we are only just starting to appreciate the long-term impact" of secondhand drinking, with the results prompting comparisons with the dangers of passive smoking.
Harm from second-hand drinking can range from the emotional stress on the drinker's loved ones and the damage done to babies born with foetal alcohol syndrome, to threats, vandalism or being injured by a drunk driver. Those aged under 25 were most at risk by someone else's drinking. Take into account the knock-on effect of alcohol-fuelled domestic violence and crime, and you get an idea of how far the damage from alcohol use truly spreads – a sobering thought as the summer has us reaching for the rosé and we let our hair down on holiday.
Being around drinkers can also make you drink more yourself, another piece of research has suggested. It put pairs of friends aged 19 to 60 into a social setting in which they had to drink two drinks. One in each pair was secretly instructed to order either an alcoholic or non-alcoholic drink. Among those told to order alcoholic drinks, the partner also had two alcoholic drinks in almost 90 per cent of cases; for those instructed to order non-alcoholic drinks the partner consumed alcohol for both drinks only 30 per cent of the time.
Like Jenny, the children of alcoholics can be some of the most profoundly affected by secondhand drinking. According to the National Association for Children of Alcoholics (NACOA), some 2.8m people in Britain have grown up with a parent with a drinking problem and more than 900,000 children are believed to be living with an alcoholic today.
"It can affect every area of a child's life," says Hilary Henriques, the charity's co-founder. Most tend to suffer in silence, not wanting to betray a parent they love, but Jenny says the suffocating secrecy that surrounded her father's drinking – and the "surreal" nature of feeling as if she was the only sane person in the house as her mother kept up the pretence of them as the perfect family – has been as damaging to her mental health as his erratic behaviour.
As the children of alcoholics begin to speak out, we are learning about the lifelong legacy secondhand drinking leaves behind. Telegraph associate editor Camilla Tominey wrote movingly about her mother's alcoholism last year, saying: "My mum was much more than an alcoholic but the drink ended up defining her." She thinks her own relationship with alcohol has been affected by her childhood experiences. At university, she sometimes drank so heavily she had blackouts. On becoming a mother, she went teetotal: "It was the only way to break the cycle. I never wanted to be drunk in front of my kids."
Josh Connolly, 32, was so scarred by his childhood experiences – one of his most vivid memories is his father simultaneously swigging from a bottle and urinating in front of families in a local park and his own sense of shame for wanting to get away from him – he turned to drink himself in his teens. Drugs too. And he continued using even after his four children came along.
"I would cause myself problems - go missing, get arrested, wake up in hospital - when the thing I most wanted was to come home from work and read my kids a story. I had a problem being with them. When I was sober I would always be thinking if I could just get that "good" drunk, just three or four to level me off, I could enjoy them. But if I had three or four drinks, I then couldn't stop," he says.
He eventually spiralled down to the point where he decided to take his own life. "It felt like a very selfless and noble decision. I thought the best thing for the children would be if I was gone. I went to see them for a last weekend and somehow, because I knew I was going to die, the past became irrelevant and the future was non-existent.
"I was present in the moment. Probably for the first time ever. I remember cuddling my daughter and looking at my boy as he went down a slide and feeling connected in a way I never had before. So I changed my mind and, ever since, I've been on a voyage of self-discovery."
He found solace and strength through NACOA, where he met people with similar experiences. "Instead of someone saying, 'Ok, you're struggling, let's get you to stop', they said, "Of course you're angry, of course you're sad'. I felt validated for the first time."
He has quit drinking, but says even moderate drinkers need to be vigilant: "Question your relationship with alcohol. You don't have to be an alcoholic to be irritable and restless around your children. What they see is that you're irritable and restless until you have a glass of wine at night. The message you're sending is, 'You're not quite good enough to make me feel good but this glass of wine is…'"
At a glance: The signs and symptoms of alcoholism
• A lack of interest in previously normal activities
• Appearing intoxicated more regularly
• Needing to drink more in order to achieve the same effects
• Appearing tired, unwell or irritable
• An inability to say no to alcohol
• Anxiety, depression or other mental health problems
• Becoming secretive or dishonest