It's not as easy as you might think to keep track of who's leaving the country

Most of the worst problems developed well before Theresa May arrived at the Home Office

Home Secretary Theresa May after a Cabinet meeting at 10 Downing Street earlier this week (Reuters)

Even in the colourful context of historical Whitehall bungles, the decade-long saga of attempts to reintroduce checks on foreign visitors leaving Britain takes some beating.

After all, the checks existed until the 1990s, so why has it been so difficult to bring them back? The answer lies in bureaucratic wrangling, changes to the plans, computer failures, legal tussles and institutional inertia.

To be fair, most of the worst problems had developed well before Theresa May arrived at the Home Office. It was as long ago as the mid-2000s that the Blair government decided to re-establish exit checks at borders as a way of getting a better idea of whose visas had run out and who was in the country illegally.

Part of its solution was a £750m “e-Borders” programme under which airlines and ferry companies would be required to collect information about the passengers they were transporting in and out of Britain.

The Coalition Government adopted the idea of reinstating exit checks and set itself a target of next year’s election for the system to be fully operational. Home Office ministers and officials insist they can still achieve that, although others in government are not so sure.

They include Nick Clegg, who has expressed his fury over what he sees as foot-dragging by the department, complaining privately about “a total lack of will to make it happen”. His view hasn’t changed and the deadline for the rollout of border checks is just 11 months away.

The Home Office says the introduction of checks on 100 million passengers a year is a far more complex operation than can be achieved by a simple snap of the Deputy Prime Minister’s fingers, but maintains it will meet the target.

But the signs are not good. The head of the UK Border Force, Sir Charles Montgomery, an old Navy man brought in to shake up one of Whitehall’s most troubled organisations, recently disclosed that the e-Borders project had been quietly “terminated”.

Instead the proposal – denounced as a “shambles” and a “debacle” by Keith Vaz, the chairman of the Commons Home Affairs Select Committee – has been incorporated into the recently launched Border Systems Programme.

This collates passenger information received from airlines and other carriers and checks it against a “warnings index” which lists suspected terrorists and criminals.

Currently information is collected about nearly 80 per cent of travellers and the Home Office faces a problem in driving that figure up to 100 per cent by next spring.

While details of about 95 per cent of airline passengers are recorded under the system, the figure is much lower for sea and rail travellers.

Ferry companies tend not to record travellers’ details, while many Eurostar tickets are sold at railway stations which lack the capacity to link in to computer systems monitoring new arrivals. And what about people who land in the UK on a private flight or aboard their own boat?

Officials have also been grappling with the dilemma of how to ensure that the compilation of information about passengers within the European Union complies with its rules on freedom of movement and data collection.

Even if full exit checks are imposed by next year, it is still uncertain whether they will capture the full range of information originally intended such as whether a visitor’s visa has expired.

Officials and ministers may be making renewed efforts to get the much-delayed system in place on time, but don’t hold your breath.