Beecham Research Laboratories at Brockham Park in 1959 discovered meticillin (or methicillin), the first semi-synthetic penicillin (beta-lactamase stable), deriving from their discovery in 1958 of 6-APA, the core constituent; the team, led by Prof George Rolinson, won the Mullard Award in 1971. Bipyridine compounds (Paraquat-Gramoxone and Diquat) were discovered for herbicide use in 1954 by William Boon at ICI's Plant Protection division at Jealott's Hill, being released onto the market in 1958. AZT/Retrovir (zidovudine) was first manufactured by Wellcome in 1987 in Kent; they also introduced Zovirax (aciclovir), and the naturally occurring digoxin, a cardiac glycoside.