Fertiliser-based explosives have proved their deadly effectiveness in a series of horrific terror attacks around the world.

Provisional IRA units used the substance in bombing campaigns in Northern Ireland and against targets in London in the Nineties.

IRA members referred to it as "Co-op Mix" because of the ingredients' wide availability.

In the new age of Islamist terrorism, ammonium nitrate fertiliser packed into a truck with plastic explosive as a detonator has also become an al Qaida trademark.

The Muslim terrorists' desire to cause maximum loss of life means the fertiliser bomb's true capacity for carnage has become horribly apparent.

Although Northern Ireland terrorists' coded warnings were erratic and unreliable - most infamously with the 1998 Omagh bombing - the Provisionals did usually offer some tip-off of an imminent blast.

In comparison, al Qaida has deliberately driven victims in the direction of a blast - notably in the 2002 Bali bombings which claimed 202 lives, including 28 Britons.

Seven men were accused at the Old Bailey of conspiring to create an explosion at a major British target using 1,300lb (600kg) of fertiliser, which they had stored in a west London lock-up.

Mark Heywood, for the prosecution, said a handbook discovered on Jawad Akbar's computer gave detailed instructions on how to make a bomb from fertiliser which was so strong it would "make the ground shake".

If all the fertiliser had been used in one device, at just under two-thirds of a ton, it would have been comparable in size to the IRA's Docklands bombs, and to the abortive attempt to bring down the Twin Towers in Manhattan in 1993.

Explosives expert and editor of NBC (Nuclear, Biological, Chemical) International, Andy Oppenheimer, said: "You would have been talking about absolute mayhem if they had aimed for an enclosed space rather than an open-air target.

"They would have had the ability to kill hundreds of people.

"They would probably have made the biggest explosion in mainland Britain since the Manchester bomb in 1996."

Mr Oppenheimer, who is writing a book on the IRA's bomb technology, added: "Using 600 kilos in one truck bomb would result in a pretty big area of destruction.

"The actual explosive yield would depend on how well the fertiliser had been milled and prepared - which was something at which the IRA were very proficient. And you can get one hell of a bang."

Jurors at the Old Bailey trial were shown a video of a mock-up bomb recreated by National Grid engineers, simulating attacks on the gas pipeline network.

The engineers used plastic explosives and then recreated a homemade bomb consisting of ammonium nitrate fertiliser and diesel fuel.

In both cases the explosion caused 300ft-high mushroom clouds and sparked fires spread 1,000ft away.

The main terrorist attacks involving fertiliser bombs include: BALTIC EXCHANGE The Baltic Exchange building in the City of London was hit by a one-ton fertiliser bomb planted by the IRA in April 1992.

The blast in St Mary Axe killed three people, including a 15-year-old girl, and caused £350 million of damage to the world's major international shipping contracts market.

Lord Foster's "Gherkin" skyscraper was later built on the site of the demolished exchange.

WORLD TRADE CENTRE The first - unsuccessful - al Qaida attack on the World Trade Centre in New York took place in February 1993.

Two-thirds of a ton of fertiliser-based explosive was detonated in Tower One's underground car park.

Islamist terrorists planned to send the tower toppling into its sister, but the seat of the explosion was not correctly located to destroy the building's foundations.

Six people were killed and more than 1,000 were injured.

Ten conspirators were convicted.

BISHOPSGATE Bishopsgate in the City of London was hit with a one-ton fertiliser bomb by the Provisional IRA in April 1993.

News of the World photographer Edward Henty, covering the story for his paper, died in the blast.

More than 40 people were injured and the explosion caused damage totalling more than £1 billion, including to the 40-storey skyscraper then known as the NatWest Tower.

The bomb - hidden in a tipper truck - left a crater 40ft wide and 20ft deep.

OKLAHOMA The Oklahoma City bombing targeted the Alfred P Murrah Federal Building in April 1995 and killed 168, although an unmatched body part suggests the toll was actually 169.

The trial of bombers Timothy McVeigh and Terry Nichols heard their motive was to avenge the US government's handling of the Waco and Ruby Ridge incidents.

Two tons of fertiliser were used, although in a more destructive compound than was deployed in many other terror attacks.

McVeigh was executed by lethal injection in 2001. Nichols was sentenced to life imprisonment.

DOCKLANDS A massive car bomb detonated beneath South Quay station in London's Docklands in February 1996.

The 1,000lb device killed two men, ended a 17-month IRA ceasefire and caused £85 million of damage.

The IRA had attempted to destroy the nearby 50-storey Canary Wharf tower in November 1992, but the detonator failed to ignite the main charge.

MANCHESTER The IRA struck Manchester city centre with a 3,300lb bomb, injuring more than 200 people.

No one was killed due to a coded warning being phoned in more than an hour before the blast, at 11am on a Saturday morning in June 1996.

It was the largest bomb to explode in Britain since the Second World War.

The bomb was contained in a lorry parked in the city's Corporation Street, between the Arndale shopping centre and a flagship Marks and Spencer store.

US EMBASSY ATTACKS Al Qaida carried out what would become a trademark simultaneous attack on US embassies in Nairobi, Kenya, and Dar es Salaam, Tanzania, in August 1998.

The blasts killed 224 people - 213 of those in Nairobi.

BALI The Bali bombings in October 2002 led to the deaths of 202 people, mainly Western tourists in their 20s and 30s.

A suicide bomber triggered a backpack bomb in a bar and a fertiliser bomb hidden in a white Mitsubishi van outside the Sari Club was triggered as people fled.

KARACHI Another al Qaida-linked attack on a US embassy - this time in Karachi, Pakistan, in June 2002.

A truck with a fertiliser bomb was driven by a suicide bomber towards US consular buildings, killing 12 and injuring 51, all Pakistanis.

ISTANBUL Al Qaida targets British interests in the Turkish capital.

Suicide bombers detonated blasts at the British Consulate and the HSBC Bank, killing 30 people including British consul general Roger Short.