The 32-year-old out-scored Steve Robinson decisively on all three judges' scorecards to sustain his world championship ambitions.
Hardy received a 119-110 verdict from Richie Davies, a 118-110 decision from referee Roy Francis and Mickey Vanns' winning margin of 117-112.
The scoring reflected the champion's command of a fight in which Robinson rarely looked like resurrecting a career flattened by Naseem Hamed, who took away his World Boxing Organisation crown nearly 18 months ago.
Hamed, who meets American Tom Johnson in a unification fight at London Arena on Saturday, is now Hardy's target following this third successful European defence.
Oliver McCall was warned to expect a drugs test soon after his arrival in Las Vegas yesterday for the vacant World Boxing Council heavyweight title showdown against Lennox Lewis.
McCall has recently undergone his third drugs rehabilitation programme, but stresses that he is "clean and sober" before Friday's rematch at the Las Vegas Hilton. "If the WBC don't test him, then we will as soon as he arrives in town," Marc Ratner, of the Nevada State Athletic Commission, said.
"Lennox will not be tested, but fighters like McCall, who have had a problem in the past, we check out. We are not suspicious of Oliver, but these things need to be done. It's no secret what we are doing. Both men will have to take a test after the fight under our rules and the WBC's."
Frank Maloney, Lewis's manager, said: "The drug rumours don't worry Lennox. We think they may be a ploy to lull him into a false sense of security. We are not going to be fooled by it. We are convinced McCall will be in the best shape of his life."
McCall took Lewis's WBC crown at Wembley Arena in September 1994, winning by a shock second-round stoppage. After successfully defending the title against Larry Holmes, McCall returned to Wembley, only for Frank Bruno to take his title.
n Naseem Hamed's manager, Brendan Ingle, has dropped his objection to the appointment of an American referee, Rudy Battle, for Saturday's featherweight unification bout against Tom "Boom Boom" Johnson.Reuse content