Appearing in the episode "A Thing or Two About Loyalty", Lambert was a friend of Guy of Gisborne and the resident chemist at Nottingham Castle. He developed the Greek fire powder, but when he refused to turn over the recipe to Sheriff Vaisey in accordance with his contract with Gisborne, fearing Vaisey would use it as a destructive weapon, he was imprisoned. He refused to tell Gisborne the location of the ledger holding the Greek fire recipe, and Gisborne in turn refused to save him from the sheriff's torture, but later concocted a plan with Marian to spirit Lambert away to Kirklees Abbey. Lambert revealed to Robin Hood the location of the ledger holding the recipe, extracting in turn Robin's promise to keep it safe for him. Gisborne found out about this exchange via the sheriff and, feeling betrayed, reneged on his and Marian's agreement to rescue him. It was with his approval that Lambert was tortured to death that night.
Lambert was portrayed by René Zagger.