For the last few months, Real Story has had exclusive access to hospitals and surgeries across Britain. We've discovered that our health system is now a magnet to overseas patients.

For some, these are the so called health tourists - people taking advantage of the free care available. But the majority are sick and cannot find or afford treatment in their own country.

The NHS maybe their only hope - but should it foot the bill?

In Lagos the programme meets Nigerians who have British GPs and come over to the UK to use the NHS.

Secretly filming one would-be health tourist leaving the plane at Heathrow, the programme times how long it takes a foreigner to access free health care. The answer will infuriate anyone who has experienced delays waiting for an operation.

The programme obtains a leaked report from one London hospital outlining the true cost of NHS tourism.

It also examines the cost of people coming to this country to receive treatment for HIV. In some clinics as many as 80% of patients with HIV or AIDS are health tourists.

The programme also exposes the Australian and New Zealander backpackers who use the NHS to subsidise their holidays.

Real Story: Monday 11 August at 1930 BST on BBC ONE and the Real Story website.