Any weapon you want, just don't ask too many questions

As a Peruvian army captain in full uniform looks on, I am squinting down the viewfinder of the Serpent, the first shoulder-launched multipurpose assault weapon I have ever handled, its crosshair fixed on a tank 291m in the far distance, my thumb poised on the fire button.

"Just send that right down and give someone a bad day," says Brian Gaume, the man selling Serpents to those with a few millions to spare and an itchy trigger finger. I do so, and, on the simulator plasma screen in front of me, a little green pixellated tank is obliterated.

At the Defence Security and Equipment International arms fair in London's Excel Centre, there is no shortage of options for dishing out bad days, weeks, months and whole lifetimes.

Yet for the thousands of military and trade delegates who will visit the exhibition this week, this is clearly a fun day out. The halls are packed, the lunch queues terrifyingly long. Only the women's toilets are mysteriously deserted.

Next year, the same hall will host the Olympic tae kwan do and boxing contests. But this week it is not the place to be for those interested in hand-to-hand combat.

Next to the Serpent, one of many developments from Raytheon UK, the British arm of the United States defence giant, is the Paveway IV, a 225kg laser-guided bomb.

"It can be programmed to explode underground, to explode over a particular car or tank, or to take out a particular floor of a building," says Nick West, the company's communications director. During the past few months, the Paveway IV's lasers have been set to guide its missiles from allied jets into strategic targets all over Libya.

Britain's Defence Secretary, Liam Fox, addressed the delegates yesterday, extending a warm welcome to the various invitees, among them military procurement officers from Angola, Bahrain and Saudi Arabia.

The 65 national delegations asked to buy weapons in London include 14 regimes defined as "authoritarian" by human rights groups, which have highlighted the use of British arms in suppressing opposition movements in the Middle East.

Fox said the fair had brought together more than 1300 defence and security suppliers - "everything from traditional defence platforms to cyber-security and counter-terrorism to commercial security, fire protection and safety".

On the canals outside, huge battleships are moored and lucky delegates race around in interceptor boats, complete with anti-tank guns and surface-to-air missile defence systems.

A little like the Venice Biennale, arms companies are grouped nation by nation in their own "pavilions". The Israel pavilion looms large, but the USA pavilion is something to behold. Men in SWAT uniforms stand between rack after rack of machine-guns.

"Securing Nations Around The World" is the slogan of AeroVironment, a company that produces "unmanned aircraft systems".

To the layman, they look a lot like drones, although, as more than one "unmanned aircraft system" manufacturer said, "We don't use that word",

They can be used to target "ships, tanks or terrorists", yet the promotional poster shows an unmanned aircraft flying above Wembley Stadium - perhaps an extreme solution to the England football team's recent difficulties.

It is not hard to spot the VIPs. They mostly wear military uniform, have big red badges saying "delegate" and wander in packs. Those from the Ukraine seem particularly intimidating. The officials hold the purse strings for some of the world's biggest budgets.

The British defence industry's section is vast and sophisticated. BAe Systems is exhibiting Adaptiv, a kind of invisibility cloak that can make a giant tank look like a simple car on enemy detection systems.

"There are economies of scale at work," said a spokesman for UK Defence.

"If the Government can help a UK company to sell big numbers of its products abroad, that company can sell them to the Government for cheaper."

Yet it seems hard to strike a deal. Not one stand will discuss price. "I'm forbidden to talk about that," is a familiar refrain.

It is not the only instance of caginess. The Israeli weapons industry's stand is lined with Tavor automatic and semi-automatic rifles. "They are used in Israel and 60 other countries," a spokesman says, but refuses to say which ones. "We cannot discuss clients but go on YouTube and you will see some interesting stuff."

The man from Glock sits behind a desk littered with revolvers. Nearby, two Portuguese delegates are aiming pistols at one another, yet my notepad seems to be the most terrifying thing the salesman has ever clapped eyes on. "I cannot say anything, I cannot say anything," he repeats.

Next door, the Swiss munitions firm RUAG is similarly elusive, but its display boasts that it makes "the UK MOD's preferred hand grenade".

The new Scout tank from General Dynamics is also here, one of four new models that will become standard British Army equipment by 2020.

Even in these austere times, the 500 to 600-tank contract will be cost up to £2 billion. After a couple of hours here, that feels like a drop in the ocean.

BOOMING INDUSTRY

* Britain has the world's second- largest defence and security sector; only the United States sells more weapons and military hardware worldwide. The British share of the global market increased from 18 per cent to 20 per cent in the past year, says UK Trade and Investments.

* The industry was worth £22 billion to the British economy in 2010, the defence trade group ADS (Aerospace, Defence and Security) claims - £9.5 billion of which was in exports.

* Saudi Arabia is by far the biggest buyer of British weapons and also the largest importer of arms globally. Saudi contracts earned Britain about £300 million last year, according to arms trade analysts at the Stockholm International Peace Research Institute.

* Behind the Saudis, the US has the most defence contracts with British firms. India, which imports 70 per cent of its military equipment, represents Britain's third-largest arms market.

* Bahrain, which was controversially invited to this week's Defence Security and Equipment International exhibition after its regime crushed an uprising in February, signed contracts with British firms worth £2.4 million this year, say figures obtained by the Campaign Against the Arms Trade.

- Independent