Exclusive Prominent British bookseller W H Smith voluntarily shut its website for emergency "maintenance" last night after being warned by The Register that it was selling a range of DIY terror manuals – such as the Improvised Munitions Handbook that offer procedures for making bombs and explosive booby-traps.

The site also offered two companion titles, Boobytraps and Explosives and Demolitions.

According to the Crown Prosecution Service, "the manual was originally written for US experts and contained diagrams and drawings as well as bomb recipes involving ordinary chemicals and products such as fertiliser."

In January 2007, a Birmingham bookshop, Maktabah, was raided and forced to close after selling the handbook and a large range of related titles. And in September 2007, an 18-year-old London student was jailed for six months for possessing similar publications.

Britain's Terrorism Act, 2006, makes dissemination of "terrorist publications" a crime at section 2. British courts have previously found similar works to be likely a useful aid for would-be terrorists.

The books originated as training manuals created by the US Army in the 1960s and have been widely distributed since, often by right-wing groups.

Fast site scrub

WH Smith's website stayed down for more than four hours as coders worked to "scrub" pages of certain titles and to create filters so that the offending books will not appear online again from automated imports of book wholesalers' catalogues.

The firm told The Register that the offending titles "were not available to purchase in-store", and that they and the publications and book descriptions had been supplied to them "through a distributor".

"WH Smith has strict guidelines on the books it sells," a spokesperson said, adding: "We have taken immediate action to remove them." The spokesperson did not dispute that titles had not been checked before being copied to their website.

"We will review our controls to avoid a recurrence," she added.

El Reg's inquiries have identified three UK wholesalers that appear to include the titles in their catalogues, making automated importation of distributors' catalogues a likely source of the tomes' appearance on the WH Smith site. We have also tracked the source of the terror titles to Skyhorse Publishing of New York, which says it publishes a "maverick list" of titles.

At the time of writing, Skyhorse titles and other editions of the controversial works are also available for sale on Amazon UK and Waterstones, Britain's leading bookseller. The Register has contacted Amazon UK and Waterstones for comment.

Jo Cox connection

After The Register discovered the books – which include instructions for making bombs and explosive booby-traps – were being promoted online without checks on their legality and without any vetting of purchasers or their intentions, we ordered copies to see if they were the real deal.

After the titles turned up, we tried again using the name of a convicted British terrorist, using PayPal and assumed identities. No alarm bells rang at retailers. The order was accepted unhesitatingly, and processed and charged, but the book was stopped from reaching El Reg after we warned the bookseller of the slip-up yesterday.

One of the manuals on sale was the Improvised Munitions Handbook, which is thought to have been purchased from a US source by the alleged killer of Brit MP Jo Cox.

The suspect, Thomas Mair, 53, from Birstall, is accused of shooting and stabbing the popular politician when she arrived to hold a surgery in the West Yorkshire town, one week before the Brexit referendum. Mair is also accused of possession of a firearm and a dagger, and of an attack causing grievous bodily harm to a passerby.

On his first appearance in court and when asked his name, Mair said "death to traitors, freedom for Britain.” Mair faces murder charges at the Old Bailey next week and will be tried under terrorism protocols that accelerate the trial process and allow extra security at the courthouse.

According to sales blurb published on WH Smith's website until yesterday, the handbook Mair had bought "demonstrates ... techniques for constructing weapons that are highly effective."

Would-be shooters and bombers were also told that the book was "straightforward and incredibly user-friendly, it provides insightful information and step-by-step instructions on how to assemble weapons and explosives from common and readily available materials. Over 600 illustrations complement elaborate explanations of how to improvise any number of munitions from easily accessible resources."

The handbook includes detailed recipes for dozens of homemade explosives, such as "fertilizer explosive", nail grenades and Molotov cocktails. Two companion titles, Boobytraps and Explosives and Demolitions, were offered by Smith's from the same American publisher as paper titles or e-books. Boobytraps includes diagrams on how to boobytrap a saucepan, a domestic kettle or a motor vehicle.

Read the comments

Online booksellers need only read comments on their own websites to understand the dangers of selling these works. One online review El Reg read reviewed Boobytraps as "not a great item to be caught with, as it is rather suspicious … I thought this was just a book telling you a history around the traps … but no … it tells you how to wire grenades to tea kettles, doors, anywhere that someone will be regularly!

“I don't suggest you get this unless you are a part of Al-Qaeda." ®