Notes on using mortars were found at the Birmingham home of a British Muslim who was arrested at the Channel Tunnel with traces of high explosive on a pair of socks in his luggage, a jury heard.
The socks, which had been rolled into a ball and attached to a pyjama cord, were ideal for cleaning a mortar bomb tube, it was alleged at the Old Bailey yesterday.
The court also heard that notes on how to use mortars were found at Andrew Rowe's previous address in Birmingham and a secret code discovered at his estranged wife's home in the city.
Rowe (34) was arrested for being a suspected terrorist as he was about to return to Britain from Germany in October, 2003.
An Army expert shown the sock ball told police an " obvious use" for it would be as a mortar bore cleaner or muzzle protector, said Mark Ellison, prosecuting.
Traces of three explosives, including TNT, were consistent with mortar bombs made in Russia, he added.
Rowe, of Maida Vale, London, denies four charges under the Terrorism Act - three that he had articles for use in terrorism and one that he made a record of information for use in terrorism.
Mr Ellison said a notebook containing 20 pages in his writing on instructions on how to use mortars was found at Rowe's previous address in Birmingham in August 2003.
The following day, he had gone to the British consulate in Amsterdam and asked for a new passport saying his old one had been damaged by washing.
After his arrest at the Channel Tunnel, Rowe's estranged wife's address was searched in Ash Road, Birmingham, where a code was discovered.
Mr Ellison said the code "made it possible to communicate in an innocent message which only spoke about mobile telephones".
Giving examples of the code, Mr Ellison said money was Nokia 3310, troublepolice was 3410, weapon 3610, airport 3310, army base 3331. The list of codes had included Sony Ericsson 7610 for explosives factory.
A draft of a letter on the other side of the secret code explained why he was travelling abroad on "mobile phone business" and said he would soon be meeting a man who needed his help, the jury was told.
Hotel receipts showed Rowe had been at the Frankfurt hotel from October 14-23 2003, where he was visited by a man.
Mr Ellison said the items in the charges were for use in the preparation of, or the commission of, terrorism.
This was in advance of the ideological or religious cause followed by militant Muslims who believed it was their duty to wage Jihad, or holy war, he alleged.
Rowe had undergone a religious conversion to become a Muslim in the mid-1990s and called himself Yusuf Abdullah, and started travelling abroad.
In 1995, in the Bosnian conflict, he was in Croatia's war zone and later told doctors he came under mortar fire and was hit by shrapnel in his legs.
In 1997, he married Shabia Tafla. They had four children and lived at a number of rented addresses before she and the youngsters moved out in 2002.
Rowe was taken off his coach by British police and arrested after presenting his passport at the British territorial section of the Channel Tunnel in France.
The sock ball did not come under suspicion for a week when a policeman decided to cut it open to look for a Sim card, said Mr Ellison.
Earlier, the judge, Mr Justice Fulford, told the jury the case had "nothing whatsoever" to do with the recent London bombings.
But potential jurors directly affected by the attacks were excused from serving on the jury. The trial continues.