The Bishopsgate Bomb: Deadly mixture that sent a wave of destruction: Tom Wilkie explains how a ton of solid fertiliser became a lethal weapon when adulterated and given a Semtex detonator with organic material

Nitrogen, nitrous oxide and steam - the most abundant gas in the atmosphere, the dentist's 'laughing gas' anaesthetic, and water vapour - were responsible for the destruction in the City of London at the weekend.

What started off as a ton or so of dense, solid fertiliser, adulterated with organic material to provide fuel for the explosion, was converted in an instant into a mixture of gases. As these expanded to fill more space than the material from which they had come, they produced a blast - a shock wave pushing the air in front of it to shatter windows and damage buildings in the surrounding area.

The blast is usually attributed to the fertiliser ammonium nitrate, but manufacturers point out that, in the form in which it is sold to farmers in Britain, ammonium nitrate cannot explode. Barry Higgs, director-general of the Fertiliser Manufacturers' Association, said: 'Ammonium nitrate is extremely safe: you could put a match under it and it would not burn.'

The IRA has to adulterate the fertiliser with some organic material before it can be used in an explosive. It also has to detonate the explosion, most probably by setting off a small charge of Semtex in the middle of the load.

In an attempt to cut off supplies to the IRA, the Republic of Ireland prohibited the manufacture of ammonium nitrate in 1973, decreeing instead that farmers should use calcium ammonium nitrate, which was thought to be less explosive.

This idea was comprehensively disproved by the bomb at the Baltic Exchange last year, when calcium ammonium nitrate imported from Ireland (rather than British ammonium nitrate) was used as the raw material.

ICI, Norsk Hydro and Kemira are the three manufacturers in Britain and they make more than 1.5 million tons of ammonium nitrate a year. An additional 500,000 tons is imported from Eastern Europe. Almost all of it is used as fertiliser and the widespread application of ammonium nitrate has been responsible for the vastly increased yields Britain's farmers have secured from their land since the Second World War.

Farmers will buy 20 or 25 tons at a time, usually from an agrichemicals supplier who may have up to 200 tons of ammonium nitrate in stock. It comes in 500kg bags, or in 50kg sacks (50kg is about one hundredweight) stacked on pallets to make up a 1.5 ton consignment.

Don Martin, technical manager for Hydro Agri (UK), a subsidiary of Norsk Hydro, discounted the idea that men with, or without, Irish accents could go into an agrichemicals supplier and hand over a bundle of used notes to buy a ton of ammonium nitrate.

'The bulk of the market is through merchants who sell to account holders - to known people,' he said.

Start your day with The Independent, sign up for daily news emails
Have you tried new the Independent Digital Edition apps?
ebooks
ebooksA special investigation by Andy McSmith
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Recruitment Genius: Web Application Developer / Software Developer

£21000 - £23000 per annum: Recruitment Genius: This software development compa...

Recruitment Genius: Brand Manager

Negotiable: Recruitment Genius: Do you wish to be part of an exciting journey ...

Anna Woodward: Anna Woodward

£25,000: Anna Woodward: My client is a rapidly expanding global company who sp...

Beverley James: Transactions Manager

£30,000: Beverley James: A fantastic opportunity has arisen for a person looki...

Day In a Page

HIV pill: Scientists hail discovery of 'game-changer' that cuts the risk of infection among gay men by 86%

Scientists hail daily pill that protects against HIV infection

Breakthrough in battle against global scourge – but will the NHS pay for it?
How we must adjust our lifestyles to nature: Welcome to the 'Anthropocene', the human epoch

Time to play God

Welcome to the 'Anthropocene', the human epoch where we may need to redefine nature itself
MacGyver returns, but with a difference: Handyman hero of classic 1980s TV series to be recast as a woman

MacGyver returns, but with a difference

Handyman hero of classic 1980s TV series to be recast as a woman
Tunnel renaissance: Why cities are hiding roads down in the ground

Tunnel renaissance

Why cities are hiding roads underground
'Backstreet Boys - Show 'Em What You're Made Of': An affectionate look at five middle-aged men

Boys to men

The Backstreet Boys might be middle-aged, married and have dodgy knees, but a heartfelt documentary reveals they’re not going gently into pop’s good night
Crufts 2015: Should foreign dogs be allowed to compete?

Crufts 2015

Should foreign dogs be allowed to compete?
10 best projectors

How to make your home cinema more cinematic: 10 best projectors

Want to recreate the big-screen experience in your sitting room? IndyBest sizes up gadgets to form your film-watching
Manchester City 1 Barcelona 2 player ratings: Luis Suarez? Lionel Messi? Joe Hart? Who was the star man?

Manchester City vs Barcelona player ratings

Luis Suarez? Lionel Messi? Joe Hart? Who was the star man at the Etihad?
Arsenal vs Monaco: Monaco - the making of Gunners' manager Arsene Wenger

Monaco: the making of Wenger

Jack Pitt-Brooke speaks to former players and learns the Frenchman’s man-management has always been one of his best skills
Cricket World Cup 2015: Chris Gayle - the West Indies' enigma lives up to his reputation

Chris Gayle: The West Indies' enigma

Some said the game's eternal rebel was washed up. As ever, he proved he writes the scripts by producing a blistering World Cup innings
In Ukraine a dark world of hybrid warfare and murky loyalties prevails

In Ukraine a dark world of hybrid warfare

This war in the shadows has been going on since the fall of Mr Yanukovych
'Birdman' and 'Bullets Over Broadway': Homage or plagiarism?

Homage or plagiarism?

'Birdman' shares much DNA with Woody Allen's 'Bullets Over Broadway'
Broadchurch ends as damp squib not even David Tennant can revive

A damp squib not even David Tennant can revive

Broadchurch, Series 2 finale, review
A Koi carp breeding pond, wall-mounted iPads and a bathroom with a 'wellness' shower: inside the mansion of Germany's 'Bishop of Bling'

Inside the mansion of Germany's 'Bishop of Bling'

A Koi carp breeding pond, wall-mounted iPads and a bathroom with a 'wellness' shower