It is great to be in the sunshine again, and also a big boost for the body. The ultraviolet (UV) rays in sunshine help our bodies make vitamin D, which is needed for strong bones and protection against diseases such as diabetes and some cancers.

But quite apart from vitamin D, the UV in sunlight also lowers blood pressure and cuts the risk of heart attack and stroke by releasing nitric oxide in exposed skin, opening up blood vessels and increasing blood flow in the body. Blue light in sunshine also boosts the immune system by releasing hydrogen peroxide in the skin, energising key immune cells known as T cells, which can then move faster to any sites of infection.

Sunlight was long used for treating wounds and infections in the days before antibiotics. Florence Nightingale argued that wounded soldiers in the Crimean war should get direct sunlight in hospitals. And in the early 20th century, tuberculosis patients were treated in mountain clinics where they were exposed outdoors to strong sunlight. More recently, UV rays have been found to kill tuberculosis bacteria, even drug-resistant strains that are becoming more prevalent.

Sunlight is an astonishing drug, so long, of course, that the skin is protected from sunburn.