Williamson, who last year wrote an outstanding biography of Tom Paine, has found in ""That Devil Wilkes,"" the radical and ribald 18th century M.P., another free spirit, indeed one whose name became a battle cry against censorship and arbitrary arrest. Perhaps the greatest virtue of Williamson's book is her portrayal of Wilkes as something more than a likable scamp and political lightweight. Once precipitated into the fray by the seizure of his paper The North Briton for ""seditious libel,"" Wilkes became a sincere and intelligent democrat. Imprisoned, expelled from Parliament, driven into exile, blackmailed and defamed, Wilkes fought back with energy, stamina and a remarkable lack of personal malice toward his enemies. In his later ""respectable"" days as Lord Mayor of London, Wilkes spoke of enfranchising ""the meanest mechanic, the poorest peasant and day labourer""; his support of the American Revolution never faltered. Williamson, dwelling on Wilkes' friendships with the French philosophes, his religious tolerance and surprising independence from party factions, emphasizes the consistent ""humanity and sense of justice"" which animated him and completely lays to rest the charge of ""opportunism"" which has plagued his reputation from that day to this. An indulgent view of Wilkes, both his womanizing and politics, but one which brings him to life in a way which Louis Kronenberger's The Extraordinary Mr. Wilkes (KR, 1973, p. 1340), for all its anecdotal zest, cannot match.