A terrorist jailed for 45 years in 1986 for plotting to blow up an Israeli plane could be released early after High Court judges ruled against the government.

Nezar Hindawi attempted to destroy an El-Al airplane carrying 370 people by planting a bomb in the luggage of his pregnant fiancée. Anne-Marie Murphy, an Irish national, knew nothing of the plot; a former chambermaid in the Hiulton Hotel in Park Lane, she later gave birth to their daughter.

The plot, widely believed to have been instigated by Syria, was discovered beforehand, and in 1986 Hindawi was handed what is thought to be the longest ever specific prison term ordered by an English court. The then Lord Chief Justice described the plan as "a foul and horrible crime."

Hindawi has been eligible for early parole since 2001. In 2009 the Parole Board recommended freeing him, despite the fact that he had served only half of his sentence.

Successive Labour and Conservative Home and Justice ministers, including Alan Johnson and Ken Clarke, refused to allow his bid for parole.

It was a foul and horrible crime Lord Chief Justice

Friday's ruling by two senior High Court judges was made on the basis that Hindawi had been subjected to "flawed and unfair" decision-making that contradicted the "principles of justice that our law has always applied in cases, however heinous a crime might be".

However, it does not necessarily mean he will walk free; a further hearing will be held to decide if the Supreme Court should make the final ruling or whether the High Court can overrule Justice Secretary Ken Clarke's decision.

Hindawi, whose legal team say he has renounced terrorism, is set to be released in 2016 and deported to Jordan if his attempt for early parole is unsuccessful.

A spokesman for the Israeli Embassy said: "We expect that one of the finest justice systems will have no truck with any attempt to downplay the severity of a man sending his pregnant fiancée aboard a flight to kill 370 innocent passengers."