To anyone driving past Erol Incedal’s car after it had been stopped by police a year ago, the everyday scene would have given no clue that they were witnessing a key moment in a case that would make legal history.

Mr Incedal, 26, thought he had been pulled over for a routine traffic offence, and the officers who searched his car gave every outward impression that he was in no more trouble than the average errant motorist.

In fact, the policemen who were running the rule over Mr Incedal’s black Mercedes on September 30, 2013 secretly planted a hidden listening device, starting a chain of events that led to the first terrorism trial to be held largely in secret in a British court.

Today, in one of the only parts of the trial to be heard in open court, a jury was told that Mr Incedal had the address of Tony and Cherie Blair in his car and may have been planning an attack on an “individual of significance” or a more indiscriminate attack modelled on the 2008 Mumbai terrorist atrocity.

Richard Whittam QC, opening the case for the prosecution, told the jury at the Old Bailey in London that they were part of an “exceptional” trial, the majority of which will be heard behind closed doors.

He said the bug planted in Mr Incedal’s car recorded him saying “I hate white people” and telling his wife he might have to switch to “plan B” after his car was searched.

When he was arrested two weeks after the initial “traffic offence” incident, police seized material including a memory card containing a bomb-making manual.

Mr Whittam said: “You will hear that he was actively engaged with another or others who were abroad. The prosecution case is that such engagement was for an act, or acts of terrorism either against a limited number of individuals of significance or a more wide-ranging and indiscriminate attack such as the one in Mumbai in 2008.”

Referring to the Blair address found on a piece of paper inside a spectacles case, Mr Whittam said that although Mr Incedal had not decided on a particular target or methodology, the address may “have some significance”.

Mr Incedal denies preparing acts of terrorism and possessing a document titled Bomb Making.

The prosecution’s opening speech gave a rare insight into the tactics used by anti-terrorism police in gathering evidence against suspects.

The jury was told that the officers searched the car and found various items of interest, including the address for one of Tony and Cherie Blair’s homes, written on a piece of paper inside a white Versace spectacles case.

Also found was an Acer laptop computer, a pocket notebook and a USB dongle. Unbeknown to Mr Incedal, who was unable to see what was going on, the officers took photographs of the evidence but did not remove anything from the vehicle. Mr Incedal was then allowed to go on his way.

Mr Incedal’s encounter with the law unsettled him, it is alleged, but he appeared to have no inkling that a bug had been planted, the jury heard.

In the two weeks that followed, Mr Incedal was recorded expressing concern that his alleged plot may have been thwarted.

The court heard that he told his wife: “Made a big mistake. There was some very important stuff in the car. If they found it, we’re f—-d.”

The listening device also recorded him saying: “I hate white people so much. I might have to destroy everything and do something else, Plan B.

“These pigs. I just feel like running them over. Everyone, even the kuffar, call them pigs.”

The jury was told that the listening device had picked up a reference to running an illegal house and a suggestion that it was “too dangerous” to carry rucksacks. Snippets of chatter also included references to Bin Laden, fatwa, Syria and jihad.

Music was being played in the background that referred to “slaughter, looking at the enemy and looking at the bodies.”

The next time Mr Incedal encountered the police, at 7.12pm on October 13 last year, the circumstances were rather different. Again his car was stopped, but this time armed officers shot out the tyres of the Mercedes on the approach to Tower Bridge to prevent him trying to drive away as he was arrested on suspicion of terrorist offences.

Once again, the car was searched. Hidden between his iPhone and its protective case was a memory card wrapped in masking tape that contained three files relating to “bomb making”, the jury was told.

They included references to latex gloves, goggles, chemicals to use and a description of how to use ground down matchstick heads. There was also a “rather comical” drawing of a bomb going off in the back of a car, said Richard Whittam QC, prosecuting.

The iPhone had been used to search the internet for “Islamic State of Iraq” in both English and Arabic.

Hand written notes in a pocket notebook stated: “Fight those of the infidels who are near to you and why do you not fight in Allah’s cause for those oppressed men, women and children who cry out ‘Lord rescue us from this town'”.

When he was arrested, Mr Incedal gave his home address in Southwark, south London, and said: “Are you going into my address with guns? My wife and kids are there.” He failed to mention that he had access to a second address in Bayswater, west London, at which he had been living for some time, Mr Whittam said.

It was there that his Acer laptop was found, as well as the white Versace glasses case and registration documents for the Mercedes.

At Mr Incedal’s home address, police found an A4 pad of handwritten notes which primarily referred to the establishment of a kebab shop business, the jury heard.

There was also a reference to “Plan A”, which appeared to concern a check list for a potential operation involving “one month surveillance”, the renting of a nearby flat, transport, uniforms and references to planning, rehearsals, action, resources and route.

A handwritten spider diagram found under the bed included the words security, intelligence, communication and recruitment. Another diagram concerned “secure communications” and “methods to communicate”.

A map detailed a route through Saudi Arabia to the Pakistan border and referred to “physical endurance and core strength”. A list for travel included an item called “cover stories”.

Details of a Skype conversation found on the hard drive of the laptop contained coded messages referring to “the use of kalashnikovs like the ones used in the attack in Mumbai in 2008,” Mr Whittam said.

One of the chats between “Fatima Hamoodi” and “Zaynab Alawi” referred to being able to send “straps”, a slang word for guns, said Mr Whittam.

It went on: “These straps are not the little ones, they are like the ones we have here u knw.”

The message then referred to a “k 1122aa shhh”.

Mr Whittam told the jury: “You may think that is short for Kalashnikov.”

It is alleged Incedal used the Fatima identity to communicate from July 2013.

The message continued: “If they are able to get this type and it works may want to do mo88m 55bayy style.”

Mr Whittam said this referred to “the use of a Kalashnikov like the ones in Mumbai in 2008.”

He told the jury: “You will have to consider first of all, what were they talking about. Was it in preparation for something and if that was the topic what was this defendant’s role in that?”

The entire trial of Mr Incedal – formerly known in the case as “AB” – was originally scheduled to be heard in secret, which would have been unprecedented in British legal history. But the decision was overturned by the Court of Appeal after a successful challenge by media organisations including The Daily Telegraph. Senior judges said open justice was the “hallmark and a safeguard” of the “priceless asset” that is the rule of law.

Only a small group of accredited journalists, including one from The Daily Telegraph, will be granted access to much of the trial but will not be able to report on proceedings. The jury has been told that some of the evidence they hear will never be made public.

A second defendant, Mounir Rarmoul-Bouhadjar, 26, pleaded guilty last week to possessing a terrorist document and is awaiting sentence.

The trial continues.