Richard Cromwell is the son of Oliver Cromwell in the Gloriana chronicle (1660). He leads the party to his father and knows the mission from the inside. After the rescue he flees with them to Suffolk.
It is revealed retroactively that Richard was not the poor creature he appeared to be, but a manipulator. He is still operating: when the group has been missing for about a month, giving no signals and attempting no rescue, it is he who has been asking after them.
The Queen’s Ukenos are looking for Richard Cromwell.