Having trained in 3D design (specialising in silversmithing and jewellery), Yeowell began drawing comics purely for pleasure, with no particular intention to become a professional artist. Having shown his portfolio to artist Bryan Talbot, he quickly found himself given work by Swiftsure (on the Lieutenant Fl'ff strip), Action Force, ThunderCats and Zoids comics. This last put him in touch with writer Grant Morrison, who then picked Yeowell to be the sole artist on new superhero strip Zenith, to run in 2000 AD beginning in 1987.
Zenith was a popular success, running to four full-length series plus many one-offs. Yeowell was headhunted by American comics companies and has worked on Batman, The Fantastic Four, The Invisibles, JSA and Starman. He continued his association with Morrison, collaborating on Sebastian O and The New Adventures of Hitler.
Yeowell's work is noted for delicate penmanship and lifelike facial expressions, with a notable economy of style that means that his work suits both colour and monochrome treatment. He works with a dip pen (Gillot 404 nib) and a Windsor & Newton Series 7 No.3 sable brush, as well as Rotring and marker pens, on 220 g/m² Daler Rowney Heavyweight Cartridge Paper.
The concentration on human features means that Yeowell's work is held to suit superhero, science fiction and historical genres equally. Recent work has included The Red Seas, an eighteenth-century pirate story scripted by Ian Edginton and science fiction Triad tale Red Fang by Steve Moore.