Health is a devolved matter dealt with domestically by the Scottish Parliament, and the Welsh and Northern Ireland assemblies. Westminster retains UK-wide powers over medical regulation and safety.
By its very name, the National Health Service has to be available to everyone.
" There will be problems in some parts of the NHS this winter. It would be foolish to pretend otherwise "
It is free at the point of delivery, and that means there is no structural limit on demand - but there is a limit on how many patients the NHS can care for.
Historically, the pressures on the service are worst in the winter when the NHS has to deal with flu epidemics and injuries to the elderly who then remain in hospital 'blocking beds' because there is no one to care for them at home.
Labour in government said that it was addressing the problem.
But Health Secretary, Alan Milburn, said in October 2000: "There will be problems in some parts of the NHS this winter. It would be foolish to pretend otherwise."
But many doctors and nurses say the pressures are not confined to winter, they say the winter crisis starts in June, and ends in June.
This winter, the NHS was not faced with a crisis, but in previous years, images of very sick patients waiting on trolleys became a familiar sight in the media, as were stories of patients being transferred to distant hospitals because no beds were available nearer home.
The debate over how to make the best of the NHS's limited resources has meant a series of reforms to the service as well as arguments on how much use the NHS should make of the private sector.
After criticism in January last year Prime Minister Tony Blair promised Britain's spending on health would rise to average EU levels within four years.
In his March 2000, Budget, ahead of the second Comprehensive Spending Review, Chancellor Gordon Brown promised an "unprecedented increase" in NHS funding - 6.1% average real terms growth in the four years to 2003/4.
The limitations of the finite funding for the NHS has led to suggestions of other ways of funding the health service.
Encouraging people to take out private health insurance is one option which is favoured by the Conservatives.
But critics say many people would be reluctant to spend their own money when they have already paid taxes to fund the NHS.
They suggest the only way to persuade people to choose the private sector would be to reduce NHS services.
Social insurance schemes, like those on the continent have been suggested - as has charging patients, which advocates say would encourage responsible use of the health service and raise revenue. One suggestion has been to charge for GP appointments.
Patients are currently charged for dental check-ups and treatments, eye check-ups and treatments and prescriptions.
Charges, however, could deter those with little money who need treatment - meaning their condition may be worse and need more expensive treatment when they finally do access the NHS.
The winter period has caused seemingly unexpected problems every year for the NHS.
In preparation for the millennium, the government set up local groups to co-ordinate services over the break. The same system was used this year.
Hospitals often cancel elective (planned) operations over the potentially busy period.
Cancer patient Mavis Skeet hit the headlines in 1999 after she had five planned operations cancelled. She later died.
Bed blocking has also been a problem for the NHS. It occurs when elderly patients no longer need hospital care, but are waiting for a place in a residential or nursing home.
In a bid to address the problem, the government has called for social services and the NHS to work more closely to ensure bed blocking does not occur.
Plans to ease demand in peak times has seen the establishment of a 24-hour nurse-run health advice telephone service, NHS Direct.
In addition a network of 36 nurse-led walk-in centres was also set up. Located near hospitals or in town centres, these pilot projects offer treatment for a range of minor conditions.
And flu jabs were this year extended from the existing limit of 65 to cover everyone up to 75. The flu drug Relenza was also made available for vulnerable groups.
One of the most practical measures of how many patients the NHS can look after is how many beds it has - though health unions point out having sufficient staff to treat patients is more important than bed numbers alone.
It concluded the NHS needed an extra 4,000 beds by 2004, and an extra 25,000 beds by 2020, just to maintain the current situation.
The report showed two thirds of general and acute NHS beds were occupied by people over 65.
It also found at least two out of every ten days spent by people aged over 65 in acute hospital beds could be better provided in facilities where patients need a lower level of care.
In addition over the last 30 years, the number of NHS beds has fallen from 250,000 to 147,000.
The Labour government has argued that the shortage of beds has been, in part, caused by the internal market system, where neighbouring health authorities planned their own bed numbers.
In the NHS Plan, Labour in government pledged 7,000 extra beds by 2004, 2,100 in general and acute wards and 5,000 in intermediate care.
In February this year, Alan Milburn announced £3.1bn would be spent on 29 new hospital developments, 11 more than in the NHS Plan.
There will also be a network of fast-track surgery centres specialising in non-urgent operations.
But the question remains as to what will happen next.
Should Labour be returned to power then there is a strong indication that the party will challenge the very nature of the concept of how public services should be operated.
The party's manifesto makes clear that it believes there is a strong case for the private sector becoming increasingly involved in the delivery of public services.
Whether this will mean that the private sector will deliver clinical services - rather than just build some of the new hospitals - remains to be seen.