Now this former cowboy hopes to bring his army of volunteer medics to a new region he believes is in urgent need: Britain.

Mr Brock contacted The Times after an investigation found that millions of Britons had no local dentist willing to take on new NHS patients. There are 24 local authorities in which every dentist is taking on only private patients, with stories of people resorting to pulling their own teeth out, drugged up on alcohol and over-the-counter painkillers.

His charity, Remote Area Medical (RAM), has put on nearly 900 such events, mostly in the US. The Times visited a clinic in Baltimore where 1,234 patients were seen in two days. A giant convention centre was filled with 100 dental chairs, supplied by RAM. Some 1,842 bad teeth were removed. Another 433 patients had eye examinations and 398 of them were given free prescription glasses.

At another recent event in rural Virginia 2,416 patients were seen in two days. The majority had no insurance cover to pay for dental work and nowhere else to go.

Mr Brock said: “It doesn’t take a rocket scientist to equate the healthcare situation in Britain to that here in the United States. Healthcare for millions of Americans is accessible but not affordable. This dilemma reaches deep into the middle class when it comes to dentistry and vision care.”

In 2015-16 in Britain, tooth decay was the most common reason for hospital admission for children aged five to nine.

Mr Brock is confident that he has a corporate donor willing to transport his organisation’s medical equipment to Britain from the US. He believes he can round up scores of American and Canadian dentists and doctors who would be willing to pay their own travel expenses and work without payment.

But he faces regulatory hurdles. If bringing in American volunteers proves too complicated he is ready to try to attract doctors from across the EU.

For Mr Brock the project would be a homecoming. He was born in Preston, Lancashire. In 1953, aged 17, he travelled to what is now Guyana in South America and for 15 years lived as a vaquero, or cowboy, with the Wapishana Indians. One day his horse threw him and his colleagues brought unwelcome news. “They told me I was 26 days away from the nearest doctor.”