Also, says Dr Harcup, bath-time can change our perceptions of our body because, when we look down at ourselves in water, we look slimmer. And it can have a good effect on our bodies themselves.
"Lactic acid is expelled much more easily, which has the effect of relaxing muscles and easing aches and pains."
A hot bath can also stimulate circulation and cell movement, and the water pressure helps to relieve organs, enabling us to relax more easily. Sally Hill, a complementary health practitioner and expert in flotation bath therapy, thinks the NHS could help to manage many common conditions more effectively with bath therapy.
"In most European countries, that is already in place. We know that flotation bath therapy can help with pain relief, inflammation reduction and sports injuries, and that regular hot salt baths can help greatly with arthritic and skin conditions, back pain, colds and flu.
"On a more general level, I think we could all benefit greatly from having regular hot salt baths - they relax and detoxify us and help get rid of all the gunk we pick up from day to day."
Hill has also helped cerebral palsy sufferers. "They experience profound relaxation through it, which helps ease muscle spasms at a much quicker rate than most other methods."
She cites an American study on delinquent boys who became calmer after regular warm baths, and says there is evidence that Epsom Salts baths can have positive, relaxing effects on autistic children. Paul Simons, director of the new Bath Spa Project, which will open early next year, says that baths have played an important role throughout the ages.
"For the Romans, bathing was a form of complementary medicine, and it was very much a central part of their fitness regime."
Bathing has been used to help skin conditions from eczema to psoriasis, and 2,000 years ago, it was thought to stop the spread of leprosy from one part of the body to another. "During the Monastic period, from the 12th century until the Reformation in the 16th century," says Simons, "the country's baths were seen as places of pilgrimage, as they were known for their healing benefits."
During the Victorian age, the "cold water cure" - prescribing a cold bath as a painkiller - was widely used. Darwin is reported to have used this method to help his insomnia. "After about three minutes in a cold bath, people actually start to relax, which is why it was often used by people who found it hard to sleep," says Dr Harcup.
The perfect bath, says Mark Carver of bath suppliers Ripples of Mayfair, is "an acrylic one - this is the most warming material - that is not too big or too small for your body. I would also advise buying a headrest."
Because a really long, hot bath can put a strain on your circulation, Morris advises lingering no longer than 10 minutes.