The first episode of the second series focuses on Britain's sexual health. In just ten years the number of diagnosed new cases of sexually transmitted infections has doubled and sexual health services account for over £1billion of the NHS budget. Lead consultant Rachael Jones and her team at the West London Centre for Sexual Health are tackling this sexual time bomb. Chlamydia is the clinic's number one diagnosis. But Michael, 25, is dismissive: 'I thought everyone gets it. If you haven't had it, you're boring. It's almost like being brought into manhood,' he says. And many in this generation don't use condoms, routinely taking risks. As 19-year-old Stacey says, 'if I have to put one on I'll put on one. If she's ok with it, I won't.' Undetected and untreated, STIs can lead to infertility, cancer and even death. Yet staff at the clinic are not only coping with high numbers of patients, but also spend much of their time trying to make their young patients realise the dangers of STIs and the importance of practicing safe sex. The clinic runs a confidential after-school walk-in service for under-19s, but staff must work quickly as patients often get bored and do not want to wait. Despite a recent miscarriage, 15-year-old Shannon is not taking her pill and misses appointments to have her contraceptive implant - a key weapon in the government's multi-million pound campaign to halve teen pregnancy - fitted, forcing a sexual health support worker to take her to the op. And, in three years, Dr Rachael Jones has seen the sudden spread of HIV amongst teenagers. Perry, 17, who has had five HIV screenings in one year, chillingly says: 'If I do have HIV it would be a bit upsetting but I'd have to live with. You can't cry forever.'

The number of knife attack victims treated at The Royal London Hospital in Whitechapel has doubled in five years. The Hospital reveals how these alarming numbers of patients are treated and the effect on NHS staff dealing with the immediate and long-term repercussions of violence between young men. The average cost of treating a penetrating injury, most of which are stabbings, is estimated at £8,000, and The Royal London treat some of the most serious cases, costing as much as £200,000. It has a pioneering trauma unit acting as a prototype for the rest of the country. When a stab victim comes in clinical staff are immediately mobilised from A & E and around the hospital. Consultant trauma surgeon Mike Walsh is the hospital's trauma director and has seen a steady increase in the number of patients who come in after being stabbed. 'The hardest thing, particularly if they die, is the sense of waste of life,' he says, 'the waste of potential and opportunity.' When Mike started at The Royal London in 1997, knife crime was responsible for less than 10% of trauma patients; now it is around 25%. The NHS spends millions every year treating victims of knife crime. For very severe injuries, intensive care and long hospital stays add up to a substantial cost. The hospital even sees patients as young as 13, such as Nigel, who has been stabbed by a group of boys in his neighbourhood and doesn't even seem surprised. Nigel says: 'We're all destined to die so if it happened it happened.'

The Hospital examines the demands for cosmetic surgery on the NHS and how they are affecting resources otherwise allocated to treating seriously ill patients. As well as curing the unwell, doctors are now expected to correct our perceived imperfections. Broomfield Hospital in Essex is home to one of the NHS's busiest plastic surgery units and the majority of their requests for cosmetic surgery are for breasts. According to national guidelines none of the cases can be purely 'cosmetic', but many of the cosmetic operations at the hospital are carried out due to non-cosmetic reasons. Popular culture is often cited as influencing teenage girls in favour of bigger breasts and the NHS is now continually being asked to draw the line between normal and abnormal sizes. But as consultant surgeon Venkat Ramakrishnan says, 'everything is subjective.' Local Primary Care Trust panels decide who qualifies for cosmetic surgery, and while national guidelines remain the same for PCTs, the interpretation of them can vary across the country, leading to a post code lottery for eligibility. 'When we see a patient who is denied an operation and a very similar patient who receives the operation it is very frustrating for us,' says consultant surgeon Venkat Ramakrishnan. 'It is very difficult for us to explain to the patient who didn't get the operation, why.' Venkat and his team perform around 40 cosmetic procedures every year and have to fit anything cosmetic that is approved into a tightly packed operating schedule.

One in five patients at the Mayday University Hospital in Croydon are there because of diabetes. The programme illustrates the difficulties in treating young diabetics, as staff struggle to make them reconcile the seriousness of their condition with their lifestyle choices. Diabetes is fast becoming the single biggest drain on NHS resources. Treating the disease and its complications currently costs £1 million every hour, using up to 10% of the NHS's annual budget, and figures are rising rapidly. 'There are 15 or 16,000 diabetics in Croydon, where I work' says Dr Richard Savine, who is treating more and more patients. 'As it is an awful lot of people who I end up taking ultimate responsibility for, I rarely think about it in those terms. I'd probably go mad if I started thinking about the size of the problem.' Due to increasingly poor diet and a lack of exercise, type 2 diabetes is being picked up in increasingly young patients, so much so that a new diabetic is now diagnosed every three minutes in the UK. NHS workers like Dr Savine and his staff are dealing with potentially a ticking time bomb of young people who, at middle age, will have heart diseases and strokes, and need kidney transplants. To target young diabetics, Dr Savine has set up a special monthly clinic. Each afternoon costs the Mayday approximately £10,000. But some patients frequently don't bother to show for their appointments. Patients like 15-year-old Francesca, who also doesn't always test her blood sugars for her type 1 diabetes, and was rushed to hospital in a diabetic coma brought on by a prolonged bout of binge-drinking. Despite this she says: 'I don't let my diabetes run my life. I do what I want to do, when I want to do it.'

For the first time in their careers, doctors are seeing people in their twenties with lifestyle-related liver disease. King's College Hospital in London has the largest liver transplant programme in Europe. The final episode of the series explores how staff deal with the vast amount of patients suffering from liver disease, the difficulties in managing the demand for transplants and their efforts to curb the surging numbers of people playing a high-risk game with their lives. Dr Kosh Agarwal is a Consultant at King's College Hospital's Liver Unit, where they have patients referred from all over the country. The most common lifestyle reason for liver transplants in the UK is alcohol-related liver disease. In five years the number of patients at King's with lifestyle-related liver disease has more than doubled. The liver unit has approximately 150 people on its transplant waiting list. A team of over 20 people has to agree on who makes the list and their weekly meetings can be fraught. 'The idea of who's deserving and who's not deserving I think is a very thorny for us as a transplant unit,' says Kosh.