How They Caught... the Tesco bomber

During the second half of 2000 a Tesco supermarket in Ferndown, Bournemouth, was at the centre of a five-month extortion campaign, which had the potential to endanger hundreds of lives and could have lost the store hundreds of thousands of pounds. It began with threatening letters from a mystery blackmailer and ended with a huge police manhunt.

On 30 August 2000, a store manager received a threatening letter that said Tesco customers would be sent letter bombs if demands were not met.

The letter started with the misspelt phrase 'Without predujice' and was signed by 'Sally', words that would be used on all future letters.

Days later the store received an identical letter, which had been charred by fire. They traced the letter to a fire-damaged postbox in the area that would later prove vital in identifying the blackmailer.

Communicating through the classified ads of the local paper, the blackmailer escalated his threats and sent a parcel to a 70-year-old Tesco customer. The parcel exploded in the pensioner's hands leaving him severely shaken.

Three more letter bombs were discovered at the local sorting office and a further seven Tesco customers received threatening letters warning that anyone seen shopping at the store would be a target. It became apparent that the blackmailer was following customers home from Tesco, and was prepared to carry out his or her threats.

The blackmailer devised a three-part code to communicate more complicated messages to Tesco and claimed they had planted a pipe bomb in a customer's garden. The blackmailer sent a map referring to an area containing 500 gardens. A mammoth search was carried out but no bomb was recovered.

The blackmailer sent another letter admitting he or she had never planted the bomb. It had been posted from the Bradpole Road postbox, the same one used to deliver the first fire-damaged letter.

The postbox had been under surveillance from the beginning of the case and police now knew their bomber was one of 38 people who used it on the day the most recent letter was sent.

Police traced the letters and interviewed some of the people who posted them and finally a surveillance officer watching the postbox recognised Robert Dyer from CCTV photos of potential suspects.

Police visited Dyer's home and a search of his computer revealed a blackmail letter starting with the infamous line "Without predujice" and signed by Sally. Police had found their man.

Dyer was found guilty of nine cases of blackmail and sentenced to 14 years imprisonment in June 2001.

• August 2000 - Tesco in Ferndown receives the first two blackmail letters, the second is damaged by fire. Police identify the postbox on Castle Lane at the junction with Bradpole Road as the only postbox in the area to suffer a fire. The blackmailer instructs the police to place an ad in the personal section of the Daily Echo.

• 6 September 2000 -The police respond through a personal ad and ask the blackmailer to call as the demands are technically impossible to fulfil.

• 19 September 2000 -A 70-year-old Tesco customer receives a bomb device in a letter. It is made from gunpowder packed in a CD case. Police recover three more letter bombs in the postal sorting office that are made safe by bomb disposal experts.

• 20 September 2000 - Seven identical letters are delivered to the homes of Tesco customers within the Bournemouth and Poole area.

• 20-21 September 2000 - The local and national media are alerted and the public are asked to be vigilant through a region-wide poster campaign.

• 22 September 2000 - Police send another message to the blackmailer in the personal ads asking him to get in contact because there are problems with the demands.

• 2 October 2000 - The blackmailer sends Tesco another letter demanding £200,000 and threatens that a next generation of bombs will go off if demands are not met by 7 October.

• 5-7 October 2000 - Police send more messages through the personal ads again saying there are technical problems with demands.

• 10 October 2000 - The blackmailer sends another letter explaining he has devised a three-part code to communicate technical issues. The letter also warns that a pipe bomb will be planted in a Tesco customer's garden, if demands are not met soon.

• 18 October 2000 - A personal ad is placed in the Echo directing Sally to a coded message on page 7. It's displayed in the main newspaper as a Mensa-style puzzle and contains a detailed explanation of the technical difficulties.

• 16 November 2000 - A further demand letter is received at Tesco Ferndown, giving a deadline of 12 December.

• 4 December 2000 - A major police search goes into operation following the blackmailer's claim that a pipe bomb has been hidden in a Tesco customer's garden. A map grid reference is given but it covers an area containing 500 houses. No bomb is recovered.

• 7 December 2000 - The blackmailer sends another letter from Bradpole Road saying the bomb was never planted but more bombs would be if demands were not met. Police had been observing this postbox and have CCTV footage showing 38 people posting 170 letters the day the blackmailer delivered their letter. The police are particularly interested in footage of a man delivering a single letter. It's unusual because he uses only the tips of his fingers. They're sure this is their man.

• 19 February 2001 - After an officer recognises the suspect at a local petrol station, police go to the home address of Robert Edward Dyer. After an initial introduction, Dyer agrees to a DNA test, and lets officers enter his home. Police examine Dyer's home computer and recover a new blackmail letter dated 15 February, 2001. Dyer is arrested and police find a set of the codes behind the gas boiler in the kitchen.

• 11 June 2001 - Dyer is sentenced to 14 years imprisonment. During his trial, Dyer, 51, said he had money problems and got the idea after reading a Reader's Digest article about Rodney Witchelo, the Mardi Gras bomber, who mounted a campaign against a supermarket and food manufacturers in 1988.