It can't have escaped anybody's notice that yesterday was the 70th birthday of the National Health Service.

The anniversary has been all over the newspapers, TV and radio, and it deserves to be. It is the greatest institution that this country will ever create.

It was born on July 5 1948 as the offspring of one single, noble principle: that everybody in a civilised, humane society should have the right to free health care.

Nobody should be left with a debilitating medical condition or denied the treatment that would save their lives because they can't afford to pay for it - when we as a society can.

It is hard for anyone brought up with the NHS to know what life was like before it. The terror that the poorest people used to face if they fell ill is something that is now only within the living memory of people well over 70.

It's still a reality in other countries - which is worth bearing in mind before we criticise it.

Of course, just like the BBC and the European Union, the NHS has always had its enemies, especially among those who are determined to believe that everything publicly owned and funded by taxes is bad and everything in private hands is good - even Northern Trains.

Fortunately the NHS has far too much popular support for them to be able to abolish it.

No politician would dare. Theresa May's birthday present of an extra £20.5 billion demonstrated that.

The Audit Office has warned that it won't be enough. But it can't do any harm.

However no amount of money could ever really be enough, because demand for health care is infinite.

In some ways modern medicine is a victim of its own success.

It gets more sophisticated, more cures or treatments become available, more doctors, nurses and other health professionals need to be recruited, trained and paid, more people live to old age and suffer the health problems it brings. That requires more money.

Prevention of course, is better than cure. And that's why I would argue that some of this extra money should be spent on public health.

Nowadays less than 16 per cent of the UK population smoke, whereas in 1974 45 per cent of people did. Heavy drinking also seems to be in decline. Public health campaigns have helped achieve that.

Now obesity is catching up with smoking as the leading preventable cause of illness - and so it's the focus of current public health campaigns.

Yet there are other preventable causes that perhaps aren't as obvious.

Social isolation and loneliness increase the risk of heart disease and stroke by 30 per cent.

Depression and workplace stress end up costing the NHS billions every year.

So does poverty. People living in poor quality housing that is cold or damp are twice as likely to fall victim to a respiratory illness as those that don't.

Healthy food is more expensive than unhealthy fare. And in the last 17 years the life expectancy gap between the richest and poorest parts of England has widened.

The links between inequality and ill health are crystal clear.

Measures that protect the environment can also bring health benefits. Insulate our homes and we'll not only tackle fuel poverty but stay warm in winter.

Grow more of our own vegetables and we'll eat more healthily. Walk or cycle to work to cut our carbon emissions and we'll also get some exercise.

Indeed climate change is the biggest threat to public health, as is already obvious beyond our shores.

Floods and famines displace people from their homes, and rising temperatures bring an increase in the insects that carry disease - so mosquitoes are being found in places they'd never been seen before.

The World Health Organisation predicts that in 12 years’ time around a quarter of a million people will be dying every year as a result of climate change.

Tackling inequality, social isolation and environmental damage are all the right things to do from a purely moral point of view.

The fact is that they could also seriously improve our health. And dealing with the causes makes more sense than dealing with the symptoms.