He is best known for his 2011 biography of King Henry VII of England, Winter King: The Dawn of Tudor England, for which he won the HW Fisher Best First Biography prize and which was the subject of a 2013 BBC documentary that he presented.
Historian Helen Castor reviewed it for The Telegraph, writing: "In broad outline, this is not a new story – but, in Penn's hands, it is a revelation...Penn has pulled off a rare feat: a brilliant and haunting evocation of the Tudor world, with irresistible echoes of the age of fear in which we now live".
[3] Reviewing it for The Guardian, Blair Worden wrote: "If Penn's interpretation can sometimes seem slanted, its exposition would be hard to over-praise.
[4] Penn was awarded the HW Fisher Best First Biography prize by the Biographers' Club in 2012 for Winter King.
[5] In 2013, Penn presented an hour-long television documentary based on his book on BBC Two.