As a result, Charles Taylor, the former president of Liberia, is on trial before the court for crimes against humanity.

Similarly, the International Criminal Court operates under a statute that "applies equally to all persons". In particular, "official capacity as a head of state or government ...shall in no case exempt a person from criminal responsibility under this statute". It is on this basis that the court's hapless prosecutor has sought, so far without success, to have President Omar al-Bashir of Sudan arrested for genocide, crimes against humanity and war crimes.

Perhaps not surprisingly, Egypt is not among the 104 countries that have accepted the court's jurisdiction. Neither is Israel or the United States. But that does not mean that their former leaders are safe.

Many countries claim jurisdiction to put defendants on trial for very serious crimes, even if they were committed abroad and even if the defendant is a foreigner. Defendants can be prosecuted for these "offences of universal jurisdiction" even if they have no links to the prosecuting state. 

Under legislation passed in 1957, it is an offence under English law to commit a "grave breach" of the 1949 Geneva Conventions anywhere in the world. It was on this basis that various Israelis have recently avoided visiting London, concerned that they might be arrested for war crimes.

No prosecution can be brought without the consent of the Attorney General but his consent is not required for an arrest warrant. Under legislation currently before parliament, the Director of Public Prosecutions would have to give his consent before a warrant could be issued.

At the beginning of February, it emerged that George W. Bush had called off a trip to Switzerland, where he was to have promoted his autobiography and addressed a fund-raising dinner for Israel. The campaign group Amnesty International said it had sent Swiss prosecutors a detailed analysis of allegations that the former US president had been responsible for authorising torture of detainees held at Guantanamo Bay. Bush has denied that waterboarding — simulated drowning — amounts to torture.

It is far too early to say whether Mubarak will face the courts. But, as Pinochet, Bashir and now Bush seem to have found, in a legally dangerous world it's sometimes best to stay quietly at home.