As a wide-screen television plays pictures of the bloody riots in Karachi across one wall of his office, Nawaz Sharif declares: “I have every intention of going back to my country.” Mr Sharif, deposed as Prime Minister of Pakistan by Pervez Musharraf’s 1999 coup, says the President “is a gone man now”.

“His options are totally exhausted and starting from today [his fall] is simply a matter of time,” he said in an interview with the Times yesterday.

Mr Sharif has had eight years to rue the day that he appointed General Musharraf as head of the army, believing him to be that rare commodity in Pakistan’s history: a military commander who would not pose a threat to an elected leader.

He was wrong, and was forced to flee to Saudi Arabia. He later moved to Dubai and, in 2005, to London. He steers his branch of the Pakistan Muslim League, the more conservative of the country’s two mainstream political parties, from a mansion flat opposite Selfridges department store. This Victorian block, with its unmarked door bells and musty carpeted stairwells. could have catered for decades of pining exiles.

The anti-Musharraf protests in Karachi that saw 41 killed and the subsequent nationwide strike may represent a chance to return. “Protests are in every nook and cranny of the country”, Mr Sharif said. “It is a positive development that people are realising that the dictator is destroying institutions.”

The trigger for the rising tension was President Musharraf’s attempt on March 9 to dismiss Chief Justice Iftikhar Chaudry on unspecified charges. But the deeper cause is his refusal to step down as head of the army, and his attempts to ensure that a new Parliament, due to be elected later this year, picks him as President.

Mr Sharif may have been outflanked in his bid to return to Pakistani politics by Benazir Bhutto — another former Prime Minister in exile and head of the other mainstream party, the more liberal Pakistan People’s Party. She has been trying to strike a deal with President Musharraf, in which he would drop corruption charges against her and allow her to return, in exchange for her party’s support in the elections. Talks appear to have collapsed, but the US has supported the notion, hoping that it might dilute the embarrassingly anti-democratic features of its ally.

Mr Sharif sees Mrs Bhutto’s move as a clear breach of a pact he struck with her in London a year ago, which “left no room for any parlays with a dictator”. But he said carefully that relations were cordial. “I keep talking to her, I try to discuss with her the implications for democracy of talking to a dictator.”

He added that “I feel personally let down by Mr Bush”, for his support of General Musharraf. Pakistan’s President “is hoodwinking the international community”, he said, “telling them that he is the only option except extremists, and that is absolute rubbish”. For the sake of courting “one man, Mr Bush is alienating 160 million Pakistanis”.

President Musharraf should have “consulted Parliament and the people” before backing the US in the 2001 Afghan invasion and the “War on Terror”, Mr Sharif continues. He is “erratic, unpredictable and impulsive — I don’t know what President Bush thinks of that.”

It is not surprising that Mr Sharif displays apparently limitless reserves of bitterness, denying President Musharraf any credit for the improving economy, or continuing talks with India.

He rejects any suggestion that he might now regret his own decision to launch Pakistan’s 1998 nuclear test, which triggered US sanctions and an economic slump. He has in the past dismissed President Musharraf’s accusations that the two Sharif governments fostered corruption.

But he is not exaggerating the depth of the constitutional crisis now facing Pakistan. He said that if elections were actually held, he would try to return to campaign, despite the unpredictable response from the Government. “London is a very nice place, but I’m looking forward to going back.”

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