What kind of NHS can Britain afford?
The next two years will see a fierce debate about immediate priorities in public spending, but many health economists are already looking 30 to 40 years further ahead.
The UK currently spends around 8% of its wealth on healthcare, mainly through the NHS.
Many economists argue that if spending simply goes on rising at a similar rate, we could be spending between 16% and 20% of our GDP on healthcare in 50 years' time.
That would have profound implications for how much could be spent by the government on other areas.
It is also likely to create sustained pressure for change in how services are delivered, to adapt to the needs of a population with more very elderly people.
The ageing profile of the population is just one of the factors likely to continue driving an increase in spending.
We are also facing increases in diseases such as type-2 diabetes, linked changes in our lifestyles which have led to more adults and children being overweight or obese.
But the contribution of technological change and medical research to spending are sometimes less obvious.
It has been estimated they contribute to up to half the increase in healthcare costs in developed countries.
Prof Ruth Newbury-Ecob, a consultant clinical geneticist at University Hospitals in Bristol, specialises in inherited heart disorders.
The mapping of the human genome has transformed her work as a doctor, allowing a more rapid transfer of knowledge from laboratory to clinic.
She is not alone in thinking we are in the early stages of a period of very significant change.
She believes that with adequate investment, genetics will become a mainstream part of healthcare within the next few decades.
She said: "Your GP will have access to this technology, be able to make an assessment and carry out a certain amount of genetic testing. And therefore be able to prescribe the right drug based on those genetic susceptibilities."
As she points out, medicines are likely to be much more targeted to smaller groups of patients. There may be pressure to spend more, but what is harder to judge is whether genetics might also deliver some cost savings by making it easier to identify risk of disease at an earlier stage in life, and intervene accordingly.
In Bristol, two hospital buildings stand as a reminder to how much healthcare is constantly changing.
The Bristol General Hospital opened in the mid-19th Century to care for the growing industrial workforce of the city.
It was initially paid for by Quaker benefactors, and like other hospitals became part of the NHS in 1948.
Now the NHS has left, and the developers City and Country are preparing the site for redevelopment into luxury flats.
I met Dr Martin Gorsky, from the London School of Hygiene and Tropical Medicine, to walk through some of the abandoned wards and corridors. He teaches those training to be public health specialists about the history of our hospital system.
It is a history of strong public engagement with communities in the 20th Century paying subscriptions and fund-raising for their local hospital.
More recently, Dr Gorsky explained, there has been a huge decline in the number of hospitals and hospital beds.
"That's taken place not so much in hospitals such as the Bristol General, but in mental health with the closure of the asylums and transition to community care," he said.
"Those hospitals tended to be on the outskirts of towns and cities, out of sight and out of mind."
It explains in part why the current wave of changes to hospital services in the NHS is often profoundly unpopular with local people.
In recent years, Dr Gorsky said, the political controversy has been particularly intense where Accident and Emergency departments are being closed or reorganised.
He said: "It's where the rational NHS planners who want to distribute resources more fairly and effectively clash with the wishes of populations."
There was no A&E department at the Bristol General to provoke those kind of protests. The transition here is one that offers a glimpse of the kind of change that might be seen elsewhere.
Neina English was the matron manager at the Bristol General and now does the same job at the new South Bristol Community hospital.
Even in the decade when the new hospital building was being planned and built, the needs of the patients were changing.
She told me: "People have more complex needs because they are living longer with different diseases, any one of which could bring them into hospital. It's very regular for us to see people in their 90s who might have several admissions into hospital."
The new hospital carries out simple day surgery, provides intensive physiotherapy for elderly people and helps those with long term conditions manage their health through outpatient clinics.
Many experts, nursing and medical organisations believe that in future more local hospitals may be more like South Bristol, with more highly specialised care concentrated elsewhere.
What many local communities also understand is that while some changes in care are being driven by the need to fit with modern medical practice, there is a strong financial motive as well.
It is not just about providing healthcare fitted to current needs, but also about trying to maintain services within an NHS budget facing intense current and future pressures.
How much the wider public understands these longer-term pressures that are likely to drive up health spending is uncertain.
Perhaps quite rightly we tend to have little grasp even of how much a visit to the GP or to A&E represents in terms of cost to the NHS.
But if the economists are right we may all need to engage with understanding more not just about the ageing population, but the other factors which may lead us to spend a bigger share of our wealth on the NHS.