A former British Airways computer expert has been jailed for 30 years for plotting to blow up a passenger aircraft.

Terrorist "sleeper" Rajib Karim - who pretended to be an unassuming software engineer - was at the centre of a conspiracy to commit a Lockerbie-style atrocity.

He put himself "at the disposal" of al-Qaeda warlord Anwar al-Awlaki, who urged him to sneak a bomb on a US-bound jet.

Middle East-based al-Awlaki wanted to commit a spectacular attack to rival 9/11 and kill hundreds of innocent victims.

Dad-of-two Karim, 31, communicated with him via secret computer messages that were so cleverly disguised it took police nine months to unravel them.

The messages - hidden in spreadsheets and packed with code words and false names - were described by cops as the "most sophisticated decryption and encryption ever uncovered in international terrorism".

At the time, Karim was working for BA in Newcastle but had access to Heathrow Airport.

He also made a failed attempt to switch to a cabin crew job to gain easier access to planes.

Bangladesh-born Karim had first come to the UK with his British wife in 2006 to seek medical treatment for their son, who was thought to have cancer.

He became a "sleeper" following his conversion to an extreme version of Islam, but tried to cover his tracks here by posing as a quiet family man.

He joined a gym and played football in a bid to blend in - and was careful never to spout extremist opinions.

His grim mission was uncovered during an international probe into evil mentor al-Awlaki, who is believed to be hiding in Yemen. Last month Karim was convicted of four counts of engaging in conduct in preparation of terrorist acts after a four-week trial at Woolwich Crown Court, South London.

He had previously admitted five other charges relating to terrorist fund-raising and offering himself as a Jihadi fighter to take on British and US troops in Afghanistan. On his return for sentencing, trial judge Mr Justice David Calvert-Smith told him: "They are matters of the utmost gravity.

"You are a committed Jihadist who understands his duty to his religion involves fighting and, if God wills, dying.

"You worked incessantly to further terrorist purposes while managing to keep your real opinions behind an unobtrusive lifestyle." Karim mouthed extremist sentiments before being escorted away.

Met Police Deputy Assistant Commissioner Stuart Osborne said the sentence reflected the seriousness of the acts Karim was contemplating, which could have had "very dramatic" consequences and "led to loss of life".