Ludwig is a BBC detective dramedy series starring David Mitchell and Anna Maxwell Martin. Wikipedia:
John Taylor (David Mitchell) is a reclusive puzzle maker who publishes puzzle books under the pen name “Ludwig”. His identical twin brother, James Taylor, is a successful detective chief inspector in the Cambridge police force. James has gone missing, and his wife Lucy (Anna Maxwell Martin), a childhood friend of both brothers, enlists John’s help to solve the mystery. Pretending to be his brother, John infiltrates the local police station to investigate; inadvertently, he becomes embroiled in solving other cases.
John’s signature serves as both his pen name’s trademark and as the logo for the show. The font is Hummingbird Bold. The opening credits use various weights of Gravesend Sans.