Nicholas Roddis, 22, caused panic when he left the device, complete with wires and a clock, in a bag on the Rotherham bound bus, after he boarded wearing a false beard in May last year.

Giving evidence at his trial at Leeds Crown Court, Roddis said he didn't think of the consequences of his actions and wore the disguise "for a laugh".

The jury heard that the hoax bomb consisted of a bag of sugar that Roddis bought from Tesco, a clock bought from eBay and wires purchased from a shop in Rotherham

Asked by Paul Watson QC, defending, what he was doing leaving such an item on the bus, Roddis said: "It was just a practical joke. I was bored, I'd lost my job and had nothing to do."

Roddis, of Reedham Drive, Rotherham, said he had made a similar device at school and his fellow pupils thought it was "right good".

"I never really thought of the consequences of it," he said.

Giggling in the witness box as he was instructed to put on his false beard and glasses in front of the jury, Roddis said he bought the disguise from eBay and used to wear it in the street because it made him look "funny".

Describing the reactions of the other passengers on the bus on Maltby to Rotherham service on Tuesday 8th May last year, he said: "I noticed that everyone was staring at me and laughing."

Asked about the bus driver's reaction, he said: "I showed him my pass and that, he was looking at me and smirking all the time."

"It was just for a laugh really," he said.

The court heard earlier in the trial that passengers noticed the defendant had left a plastic bag on the bus when he got off in the Herringthorpe area and opened it to be confronted with the device.

The bus and neighbouring houses were evacuated and an Army bomb disposal team blew up the package before the soldiers found it was a fake.

Edward Brown QC, prosecuting, told the jury a note was found with the hoax bomb which said, in badly written Arabic: "There is no God but Allah. Mohammed is the messenger of Allah. Allah the Greatest. Allah the Greatest. Allah the Greatest."

He said the note went on to say: "Britain must be punished" and was signed "The al Qaida organisation in Iraq".

Roddis told the court that he wrote the message using a translating tool on the internet and when asked why, he said: "I was on the internet in the library eight hours a day and I was bored."

The court also heard that Roddis took replica bullets he bought from eBay and railway box signals he'd taken from unlocked trains to show friends at his former workplace.

He told his former colleagues that the bullets were real and the box signals were landmines.

"I thought they'd be impressed by them," Roddis told the court.

"I was just showing off. It was stupid."

Mr Watson asked him: "Was it your intention at that time, either then or at a some future time, to do something to cause somebody serious harm or cause serious damage?"

Roddis replied "No. Not at all."

The defendant was arrested on Tuesday 10th July last year when he went for a job interview in the building where he used to work and his former manager called police because he was concerned at seeing him with a bag.

Police found items including articles on bomb making, extremist literature, acetone, hydrogen peroxide, a quantity of nails and the false beard when they searched his lodgings.

Roddis is charged with a number of terror offences, including placing a hoax bomb on a bus, engaging in the preparation of acts of terrorism, possessing articles for terrorism purposes and collecting information useful for terrorism.

He denies all the charges. The trial continues.