At Antwerp he assisted Walter Van Beirendonck, Alexander McQueen, Vivienne Westwood and Dirk Bikkembergs. The label debuted womenswear in 1999 and menswear in 2000, moving its studio from Antwerp to Paris in 2002 — the same year Willhelm became creative director of Capucci through 2004.
His work is typified by craftsmanship, eclecticism and irony, drawing on South German folklore, historical costume, sport and Japanese dress. He favours installations and tableaux vivants over the catwalk, has dressed Björk for her Volta tour, and has collaborated with Camper, MYKITA and Henzel Studio. The team has been based in Los Angeles since 2013.