Roma facts

Estimated 12m Roma worldwide Originated in Punjab, India Migrated west in several waves over 1,000 years Distinguished by blood and language 500,000 killed in Holocaust Source: Patrin

They turned away a number of Roma - commonly known as gypsy - families, including one comprising more than 10 members.

A Home Office spokeswoman said it was the first time such controls, which were agreed with the Czech Republic Government in February, had been put in place.

David Broucher, UK ambassador to the Czech Republic, added the move was to stem "the continued, systematic abuse of our immigration and asylum system by some Czech citizens."

All passengers on flights to London - including British nationals and passengers from other European Union countries and the United States - will be subject to the checks, Mr Broucher said.

Those who give unsatisfactory answers to immigration officers may be turned away.

But Mr Broucher said the immigration checks were "not a step towards a visa regime".

Unprecedented move

The Home Office spokeswoman said the controls were a "flexible response" to high numbers of passengers travelling from Prague and subsequently found not to be eligible for entry to Britain.

She described the operation as a "pre-clearance" system.

"We hope it will be a short-term thing, but it will depend on the success of it," she said.

A similar system was once part of an experiment in New York in the 1980s, she added.

She said 1,230 people arriving from the Czech Republic had claimed asylum in Britain last year, and 515 applications had been received by the end of May this year.

The number of successful applications was "very small," she said.

Discrimination complaints

There are estimated to be approximately 200,000 Roma gypsies in the Czech Republic - nearly 2% of the population.

Roma often complain of discrimination and suffer frequent racially motivated attacks and high unemployment in the republic, and elsewhere in eastern Europe.

They often leave for the West, mostly Britain, in hopes of a better life.

But Mr Broucher said there is virtually no chance for a Czech citizen to be granted asylum in the UK because the authorities do not believe they are subject to persecution by the state.

Instead, both the Czech and the UK governments see them as economic migrants.