The appellants in this case owned land that was being used by them as a caravan site within the ambit and application of the Caravan Sites and Control of Development Act 1960.  The respondent local authority issued a site licence in 2001, purportedly pursuant to the provisions of the Caravan Sites and Control of Development Act 1960.  At the time the site licence was issued there was no planning permission or equivalent granted pursuant to the provisions of the Town and Country Planning Act 1990 and therefore that licence had been illegally granted in error.  The site licence was transferred to the appellants in 2008.  In 2009, the local authority granted the appellants a certificate of lawful use and development in respect of the site pursuant to the Town and Country Planning Act 1990.  The local authority could lawfully grant the appellants a valid site licence and the appellants were invited to apply for such a licence and were told that it would be granted if they applied.  They did not do so and were therefore prosecuted by the local authority for operating a caravan site without a valid licence.  The district judge found that the licence was invalid and was therefore a nullity and of no effect for the purpose of the proceedings.  The appellants appealed.

The appellants argued that the local authority could not succeed in a prosecution where it sought to rely on the unlawfulness of its own act in granting a licence in 2001 and therefore the licence granted by the local authority had to be treated as valid and the prosecution was therefore fundamentally misconceived.

The appeal was allowed.  The court accepted the primary submission of the appellants, as the local authority was unable to show any instance where a prosecutor was entitled to rely on its own unlawful act to found a public prosecution.