Nawaz Sharif believes that he is the most popular politician in Pakistan by such a margin that he can defy the house arrest order and march on the capital with thousands of his supporters. He may well be right: even though Asif Ali Zardari wriggled through to the presidency six months ago, Sharif has long looked to be in the strongest position because of his bedrock in the Punjab.

If he does manage to oust Zardari and get himself or his party in control, it might bring some short-term stability. But unless Sharif has radically changed in character since his two spells as Prime Minister, it does not promise stability for Pakistan or for its relations with the West.

Sharif has made a career out of unpredictability, with a conservative tinge. The best that can be said of him is that, as the son of an industrialist, he marked Pakistan’s decision to elect a leader free from ties to either the military or landed aristocracy. In office (1990 to 1993, and 1997 to 1999), he put his country on a path of business liberalisation that won applause from the International Monetary Fund and World Bank and triggered much faster growth.

The worst is that he courted Islamic groups to stay in power and is himself religiously conservative; that his promotion of Pakistan’s nuclear power – and nuclear testing – inflamed relations with India just as he was exploring peace; that his governments were dogged by corruption allegations; and that no ally could count on him. Sharif has always given the impression that it is his destiny to lead his country (which is too well endowed with such people). Exiled by General Musharraf in 1999, he spent the years first in Saudi Arabia and then in a dark flat opposite Selfridges in London, brooding and plotting revenge on the military chief whom he had appointed and who had overthrown him. When interviewed, he was unable to concede that the general had done anything right or that he himself might have done anything wrong.

When public unrest against Musharraf in September 2007 forced the military leader to allow Sharif and Benazir Bhutto to return, Sharif could barely contain himself as he declared himself ready to run for office.

Musharraf briefly deported him again, to Saudi Arabia, a stagy piece of humiliation that seemed to puncture the Sharif ebullience, but he returned to contest the 2008 elections, delayed by Bhutto’s assassination.

He came in slightly behind Zardari, her widower, but always stood to be the real winner from a return of democracy because his political assets far outstripped those of his rivals.

As leader of the Pakistan Muslim League Sharif has his power base in the Punjab, Pakistan’s wealthiest and largest province, where the army has its roots. He is the son of an owner of an iron-sugar-textiles conglomerate (which, his critics say, grew much richer during his time in office). The US and Britain have treated him warily, remembering his moves to make the Prime Minister unsackable and for his attempt to make the country observe Islamic law (the Senate voted it down).

In recent weeks, he has rejected charges that he is too willing to do deals with religious extremists but, confusingly, talked of the need to compromise. That simply drives home the message that it is hard to know, in power, which way Sharif might jump.

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