His campaign against ID cards began when he was stopped by the police for speeding in Ballards Lane, Finchley on December 7^th 1950. Police Constable Harold Muckle asked to see Willcock's Identity Card and when this was request was refused the policeman tried to give him a form demanding that he should produce his ID card at a police station within two days. According to police evidence Willcock was reported as saying : " I will not produce it at any police station and I will not accept the form." When PC Muckle then tried to give him the form Willcock threw it on the pavement from where it was retrieved by another constable who put it in Willcock's car.

       Willcock was true to his word and did not report to a police station. His defiant stand therefore meant he was charged with an offence under Section 6(4) of the National Registration Act and summoned to appear before local magistrates. At this hearing Willcock argued that the emergency wartime legislation authorising ID cards was no longer valid since the emergency no longer existed. Although Willcock was found guilty the magistrates showed considerable sympathy for his arguments and he was given an absolute discharge.

           Willcock, however, was not prepared to let the matter rest and assembled a team of top lawyers to launch an appeal in the High Court (June 1951). The case was heard by seven senior judges and though Willcock lost the appeal Lord Chief Justice Goddard gave him a moral victory by stating that the magistrates had acted correctly in giving him an absolute discharge and that the police practice of routinely demanding to see a person's identity card was "wholly unreasonable". Furthermore, the court did not award prosecution costs against Willcock.

Lord Goddard went on to declare:

" To use Acts of Parliament passed for particular purposes in wartime when the war is a thing of the past tends to turn law-abiding citizens into lawbreakers."

        Willcock may have lost his court cases but he was not a man to give up easily. Supported by fellow Liberals he launched a campaign outside Parliament to get identity cards abolished. To draw attention to his cause he ceremonially destroyed his own identity card in front of press photographers on the steps of the National Liberal Club in London while in August 1951 a public meeting was held in Hyde Park to launch a petition to Parliament. Faced with a growing campaign against identity cards and the stinging criticisms of the Lord Chief Justice the incoming Conservative Government of Winston Churchill took action. On 21^st February 1952 they announced that the public would no longer be required to carry the cards although to save face they announced this as a cost-saving measure rather than one of principle.