He has survived assassination attempts, guided his country through political turmoil at home and abroad, but now President Pervez Musharraf faces the most serious challenge to his leadership since he took power in a bloodless and popular coup eight years ago.

This time the threat to his regime does not come from militant Islam or his many political rivals, but rather from the unlikely figure of a middle-aged and highly respected lawyer whose stand on a matter of principle has united the opposition and shaken the regime.

Iftikhar Chaudhry has been suspended from his post as Pakistan’s Chief Justice. He is under house arrest in Islamabad and faces unspecified charges of “misconduct and misuse of authority”.

Most suspect that the real reason for his removal was the threat that he posed to General Musharraf’s future tenure. By law the Pakistani head of state is obliged to relinquish his control of the military this year. Mr Chaudhry had made it clear that he would block any attempt to change the constitution and allow General Musharraf to hold both posts.

“I had an easy way out by resigning. But I decided to protect the respect of the judiciary and my professional honour,” he said in an interview in today’s Nation newspaper.

“How would I face my fellow judges, the lawyers community and my children? They all look up to me. Had I caved in, they would say that I talked a lot but when the time came, I could not take a stand,” he said.

No one is suggesting that Mr Chaudhry poses an existential threat to Gen Musharraf, but with elections due later this year he could badly damage the leader’s standing.

Pakistan’s domestic troubles are being closely watched from abroad, where there is evidence that attitudes are hardening towards General Musharraf from his traditional supporters in the West, particularly America and Britain.

Both countries are now committing more troops and resources to neighbouring Afghanistan, where many suspect that the Taleban insurgency is being supported from militants in Pakistan with the tacit support of the Pakistani intelligence services.

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