I hate to be the bearer of bad news, but if you’ve been looking forward to the March 27 opening of Heathrow’s Terminal 5, the new home of British Airways, you’d best sit down. The £4.3 billion facility, which has been peddled as the panacea for all that ails the modern air traveller – such as overcrowded terminals, unbearable queues and unjustified delays – is architecturally uninspired and some way off being operationally efficient.

I know because I’ve seen it – not as a guest on a champagne-fuelled media junket, but as a volunteer participant in one of the T5 trials organised by the airport’s operator, BAA.

I didn’t expect everything to be perfect: after all, the very purpose of this, and dozens of further trials between now and March, is to identify the glitches so they can be made good before the terminal goes operational. But I was expecting something new: a solution, perhaps, to the miseries suffered at Heathrow’s older terminals.

And that, as yet, is not in evidence.

For this trial, I was “booked” on BA’s 11.35am to Edinburgh.

My mission was simply to check in, pass through security and board my flight.

Despite the scale of this satanic mill, the check-in area offers little sense of space. Clusters of self-check-in booths sprout from the floor, but they seem surprisingly thin on the ground, creating the impression of a giant amusement arcade with far too few machines. Apparently, this is the fault of the International Air Transport Association (Iata).

“Iata wants everyone to check in online,” confided a BA employee, “so we predict that most people will print boarding passes at home and move straight to the bag drop.” I predict a riot. About 40,000 passengers are expected to use the terminal daily when it opens. On the day of the trial, there were just 228 (and the number of staff working was scaled down accordingly). It took me eight minutes to check in, queuing first at the self-service booth, then at the bag drop.

It took a further five minutes to clear passport control, primarily because border staff now need to take my fingerprints, using technology that still needs fine-tuning. “It works first time about two times out of three,” the clerk admitted.

So, what’s the point? “International and domestic passengers use the same departure lounge,” he explained. “That way, everyone gets to use the same shops and facilities. Because the passengers are mixed, we have to make sure only those with a right to be in the country board flights to other destinations in the UK. So, if you’re on a domestic flight, we take your fingerprints here and again at the gate.”

Next came security, the acid test of modern airport functionality. BAA says that there are 21 screening gates here in the north zone, but for our purposes only three were open, giving passengers time to admire the new tray-return system, which looks as if it was patented by Wallace and Gromit.

Trays containing personal effects burst from the scanner and proceed at high speed towards a yawning hole at the end of the conveyor. Panicked passengers dash after their possessions, unaware that an overhead sensor detects trays containing items and stops the belt before they are swallowed. It would be brilliant, if the sensor weren’t so sensitive that it brought the entire contraption to a halt every time it detected a microscopic fragment of lint – or cheese.

As I waited for harassed security staff to check my bag, high-tech billboards promised “High Definition Targeting”, but this was nothing to do with streamlining security. Sponsored by the terminal partner JC Decaux, the ads referred to the precision promotion of luxury goods to a captive market.

And captive is the appropriate word – it took 35 minutes to clear security, giving me ample time to survey the cavernous split-level departure lounge. Carluccio’s stands next door to the scanners. Harrods is across the corridor. Paul Smith, Prada and Bulgari will open downstairs, and somewhere in this upmarket shopping mall, there will be a Gordon Ramsay restaurant.

Beyond the bling, however, the Terminal 5 experience remained depressingly familiar. The seats were still sticky, the queues were still serpentine and, by the time my hand luggage had been scanned, searched and swabbed, I had little time to explore what BAA has dubbed the “stunning new gateway to the UK”.

“You’re too late,” barked the BA clerk as I arrived, breathless, at the gate. “You won’t be going to Edinburgh today.”

I wasn’t the only one. Of 228 volunteers, 31 – or 14% – failed compliance, which is BAA’s way of saying they missed their flight. It might have been more if the shops were open.

BAA is taking these trials seriously. Executives admit that the terminal will still be a building site on the March 27 opening date, but their greatest concern is its operational efficiency.

“The failure rate is still far too high,” a clipboard-carrier confided. “We can’t change the building, so all we can do is revise procedures and retrain staff. Expectations for this terminal are extremely high – and we’ve got 16 weeks to get it right.”

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