Scott Parker, 43, used a pet transportation business as a cover for smuggling the high-purity drug, stashing it inside the crates used to carry the felines.

The crime was blown open when staff at Heathrow Animal Reception Centre noticed that the pens were unusually heavy.

When they were examined, officers found compartments concealing packages – which contained a total of nine kilos of the Class A drug – in their bases.

Parker had no idea his haul had been discovered and was arrested on November 21 last year as he waited to collect the cats following the flight from Johannesburg, the National Crime Agency (NCA) said.

The cats were later reunited with their owners, who were completely unaware their animals had been used as a front for smuggling.

Parker, who worked for a company which specialised in transporting animals by air, admitted attempting to import a class A drug at Isleworth Crown Court in west London.

The London-born dual national who was living in Benoni, Gauteng, South Africa, was sentenced to seven-and-a-half years imprisonment.