For it has emerged that none of the high-powered VIP vehicles supplied by the PSNI has undergone full - and recommended - ballistic tests.

Tests are carried out separately on the specially manufactured glass and steel for all armoured cars.

But no final test is conducted once the vehicle is assembled and the various protective parts, including panelling and dashboard, welded on.

One expert told us: "If you take a lot of parts and weld them together the heat may soften them, perhaps enough to allow a bullet to penetrate a weak part of the vehicle.

"At that stage under European guidelines a further ballistic test would be carried out to identify any weak spots and modify them. This final test is not carried out by police in Northern Ireland."

Again, according to manufacturers, police here insist that the thickness of steel should be 5.5mm, whereas 6.5mm is the recognised European standard.

Some of the embarrassing issues were raised when local businessman Jim Kirkpatrick and the company he heads, NI Sheet Metal Works, won a bumper payout from the PSNI last October.

The firm, which has been manufacturing armoured protection for police vehicles since 1982, was informed it was being stripped of one deal with the work awarded instead to an English firm.

Mr Kirkpatrick's company challenged the decision through the High Court and won a £400,000 settlement.

The judge in the case also called for a criminal investigation into suspicions that "person or persons" within the PSNI had deliberately undermined the Belfast firm, through unjustified criticism of the quality of its steel.

A Fraud Squad probe was launched and two civilian workers suspended. But the saga still rumbles on after a lengthy tendering process to replace the police contract was also suspended.