[4] He was an eminent lawyer, Solicitor-General (1671), Attorney-General (1673), and Chief Justice of the Common Pleas (1675), and in 1679 was made a member of the Privy Council Ministry and, on its dissolution, of the Cabinet.

Guilford sat as a judge at some of the Popish Plot trials, and like his colleagues, he has been accused of excessive credulity in believing the lies of Titus Oates and the other informers.

North presided at the trial of one of the more disreputable of the Plot informers, Stephen College, nicknamed "the Protestant joiner", for high treason, in August 1681, and virtually ordered the jury to convict him.

[9] North's conduct of the trial attracted a great deal of criticism, as the evidence of treason (College was accused of appearing in arms at the Oxford Parliament) was considered by many to be flimsy, and the charge had already been thrown out by a grand jury.

[11] He has been criticised for remaining in office after Wright was made Chief Justice over his vehement objections, especially as it must have been clear that he no longer had any influence over judicial appointments.

Guilford was generally respected for his integrity, (apart perhaps from his conduct of the trial of Stephen College), but he was sometimes accused of self-importance and a lack of any sense of humour; for example, he showed excessive agitation at the ridiculous rumour spread by Sunderland and Jeffreys that he had been seen riding on a rhinoceros.