John Lambert was a Calvinist theologian and martyr for the Protestant cause, as well as a former friend of Thomas Cromwell. Appearing in only one episode of The Tudors, "Search for a New Queen", he is played by Ben Price.
In 3.06, Lambert is accused of heresy for denying the presence of Christ in the Eucharist. King Henry VIII, although having broken his own church from Rome, has done little to change England's religious doctrines from Catholicism, spurring further demands for reform from sects such as Calvinists and Puritans. Lambert, having been long under the eye of the conservative Bishop Gardiner, is quickly found guilty and imprisoned in the Tower of London.
While awaiting his execution by burning, Lambert is visited by his former Caimbridge classmate (and fellow Reformist), Thomas Cromwell, who is now Henry's First Minister. Cromwell, seeking both to spare Lambert an agonizing death and secure another voice for the continuing of the Reformation, urges him to recant his 'heresy' so that he will be pardoned. Lambert, however, refuses, claiming he must set an example for other Reformists not to sell out their beliefs in order to be spared pain. Cromwell argues that keeping said Reformists' voices alive is more valuable to their cause than setting an example, but Lambert remains adamant; saddened, Cromwell leaves. He later watches with dismay as Lambert is burned at the stake, screaming "None but Christ, none but Christ!".