During the reign of Henry VIII (r. 1509–1547), the statute books had proliferated with legislation creating numerous new forms of high treason.

Article III reads: "No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court."

[11] During the passage of the Treason Bill through Parliament in 1945, the Home Secretary, Sir Donald Somervell, explained the repeal of the rule as follows: It is, presumably, based on the idea that one witness may be unreliable, whereas, on the other hand, if you allege two overt acts, and if you have one witness of each, then the two unreliabilities are taken as adding up to a sufficient certainty.

Section 19 stipulated that a prosecution for treason consisting only of "open preaching or words only" must be brought within 30 days of the offence (or six months if the accused was outside the realm).

Section 20 of the Act put the common law offence of misprision (concealing) of treason on a statutory basis.