Dick Cheney has forged a reputation as the most powerful but also least visible vice-president in recent history. In the next few weeks, however, he will be forced to fight some of his battles in the open – in the courtroom and on Capitol Hill.

The first test will come in the criminal trial of his former chief of staff, Lewis “Scooter” Libby, charged with lying to a grand jury during an investigation into how a CIA agent’s name was leaked. The trial, due to begin in two weeks, is likely to set an ignominious precedent when Mr Cheney becomes the first vice-president to testify in a trial.