There’s no cure for the condition, but regular medication can help keep symptoms under control.

It is hoped combining the two drugs into one will make it easier for patients to treat themselves.

Professor Tim Harrison, an asthma expert at Nottingham University who was involved in the trial, said: ‘This could lead to a dramatic reduction in the number of asthma attacks we see. These can lead to hospital admissions and occasionally deaths.’

The trial split more than 3,000 patients into two groups.

One group was given the new inhaler – known as PT027 – and the other continued using their regular blue and brown inhalers.

By the end of the trial, the patients using the PT027 inhaler had a 27 percent reduced risk of a serious asthma attack.

The PT027 inhaler is currently pending approval by US health chiefs, and Prof Harrison says he hopes that it will become available to asthma sufferers on the NHS in due course.

Brian Johnson, 45, from Keyworth, Nottingham, took part in the trial having suffered from severe asthma since he was a child.

The married director of an engineering company said that he noticed marked improvement in his symptoms, adding: ‘I would very happily change over to using it full-time.’