The Metropolitan Police has London on a “severe” threat level. That means a terrorist attack is “highly likely”. To counter the bad guys, Britain has invested more than any other country to make its streets safe, be that with security bollards to protect pedestrians or beefed-up surveillance technology.

UK equipment makers who cut their teeth during the IRA threat are world leaders but other countries’ firms are capitalising too. Here are some of the mini industries flourishing from the terror threat.

NEVER MIND THE BOLLARDS

The most visible presence of London’s anti-terrorism drive are the bollards strewn around the capital’s tourist venues to make places such as the Palace of Westminster resemble Baghdad’s Green Zone.

The biggest, and ugliest, are known in the trade as “barges”. From above, they’re shaped more like canoes, with sharp points fore and aft to block lorry or car attacks and bombs. Made by Tata Steel Security, they consist of waist-high thick metal on the outside, filled with concrete. The barges, which work alongside Tata’s bright yellow pedestrian arches, are used widely because they are quickly and easily transported and deployed from the government stockpile in Suffolk. Tata does not break out sales or profits from its security business.

Security experts say the hideous look of the Tata system is part of its charm: it is a visible response to the terror threat that says the police are on high alert.

Less of an eyesore are the Westminster bollards: the slim, black-painted bollards often featuring the Westminster crest or that of other boroughs, depending on the geography. They’re made from manganese steel by ATG Access, a Liverpool company backed by private equity firm LDC. ATG also makes the cylindrical telescopic bollards that rise or retract from the road to block or open access. Bare concrete bollards of the type widely found on the Continent can do more harm than good in an attack because they splinter into deadly shrapnel if blown up.

Sales and marketing director Gavin Hepburn says: “It feels a bit bad saying terrorist tragedies are boosting our business, but I’m afraid it’s true.” Sales have grown from £12.5 million in 2015-16 to an expected £20 million this year. Last year, the company made £1 million profit and paid a £2 million dividend, with a growing order book overseas.

Other big players in perimeter security are stock market-quoted Hill & Smith and pavement-maker Marshalls, although they do not separate out their security revenues.

EYES (AND EARS) IN THE SKY

Ask the police or security services about aerial surveillance and you’ll often meet a flat “no comment”. But listening to and watching us from above has become big business for a small group of specialist companies.

Stock market-quoted Gama Aviation likes to talk of how it flies the world’s super-rich on private jets. It is less vocal about a more sensitive piece of work: a £4 million, four-year contract to service a new breed of police surveillance aircraft. In January, the first of four new Vulcanairs, capable of staying in the air for 10 hours at a time, will be delivered, kitted out with the latest surveillance gadgetry by Airborne Technologies.

Also shy about its services in this field is 2Excel, a firm that reputedly runs surveill-ance planes for the military, along with its more conventional civilian work. Run by ex-RAF pilots, 2Excel’s turnover leaped from £11 million to £18 million last year and it made a £2 million profit. Security researcher Alan Turnbull of website secret-bases.co.uk says 2Excel’s planes sometimes switch their transponder codes — signals used to identify planes to air traffic control and other pilots — to military IDs on some “spook flights”. 2Excel did not return calls or emails.

Turnbull said the Metropolitan Police uses secret Cessna spy planes registered at the Civil Aviation Authority to a firm called Nor Leasing. The company gives the address of a Mailboxes Inc PO Box branch in Surbiton and is not registered at Companies House.

Turnbull’s research suggests MI5 has its own surveillance planes which carry out similar operations.

Drones are increasingly being used as an additional tool by police and other authorities. The Met is trialling the Skyranger surveillance drone made by Canadian manufacturer Aeryon. Sussex police are also using it to patrol Gatwick airport. Having cut its teeth in battlefield drones for the military, the Skyranger is designed to work in all weathers and conditions. In 2015, Aeryon secured $60 million of funding from Uber backer Summit Partners. It recently expanded its UK sales and support team, citing Britain’s position as one of the biggest users of unmanned aircraft. Skyrangers carry a zoom and an infrared camera but Aeryon does not rule out other payloads in future, such as mobile-phone jamming or listening and data capture devices.

CANDID CAMERAS

The jury is out over CCTV’s usefulness in counter-terrorism. Some say it acts as a deterrent and makes it harder for suspects to meet and prepare for their attacks. Others claim that it is only really useful to find culprits after an incident.

Controversially, the biggest maker and supplier of CCTV in the UK is a vast Chinese company, Hikvision, whose biggest shareholder is the state. Nigel Inkster, the former director of operations at MI6, has said he is concerned about Chinese intelligence services potentially using its cameras here for “malign purposes”.

Hikvision’s UK operation is run by general manager Jian Yang. Still only 27, he was made a director when he was 24 — just four years after leaving Zhejiang University. The UK division is only there to service customers but has nearly trebled in size over the past year, with turnover up from £1 million to £2.6 million. Camera sales are booked through the tax-lite Netherlands, and no UK revenues or profits are available.

Automatic number-plate recognition (ANPR) is a growing part of the police and security services’ anti-terror armoury. Stock market-listed defence group Petards runs the Metropolitan police ANPR. While not declaring its revenues from the technology, a glimpse can be seen in the sales of a handheld ANPR devices business it bought last year called QRO; in the first eight months under Petards’ ownership, QRO brought in revenues of £1.2 million.

CSI LONDON

Investigations into and after terror plots invariably rest on the forensic examination of phones and computers. Israel-based Cellebrite and Micro Systemation of Sweden are two of the biggest providers of the code-cracking software that can access the data on these devices, even if blown up, thrown in rivers or otherwise largely destroyed.

Cellebrite made UK sales of £4.6 million last year, and Micro billed UK clients £3 million. It bizarrely claims to supply “97%” of Britain’s 43 police forces.

GUNS 'N' AMO

The Met increased spending on weapons and ammunition sixfold in the past year, largely because of the terror threat. In response to a Freedom of Information request, it said it spent £9.4 million on guns, bullets, Tasers and smoke and stun grenades as the force builds back up to 2010’s level of having 7000 firearms officers.

Taser is made by US company Axon and does not state UK sales or profit figures, but the Met doubled its purchases last year. A recent tender document states that the Met uses pistols from Austrian firm Glock, German Heckler & Koch carbines (pictured above, left) and US-made SIG Sauer assault rifles (above, right).

The only British weapon it uses is Accuracy International’s sniper rifle. AI’s profits jumped this year to £494,000 from £364,000 a year earlier on revenue up £1 million to £13.2 million, although UK sales were broadly flat at £2.3 million.

Terrorists hope to cause damage to cities’ economies. But in London, at least, they are only helping more companies make money.