King Rat's castle goes on sale – for $33 million

The lavish castle that became a gilded cage for Belgium's controversial wartime king has been put up for sale for AUD$33 million.

The 136-hectare estate of 'Argenteuil', near Waterloo, comprises a castle, park, chapel, forests and meadows, reports The Telegraph.

It has attracted offers in recent years, including Russian President Vladimir Putin, but were rejected.

Belgium's King Leopold III – who became hated by his countrymen for his reported collaboration with the Nazi occupiers in World War II – retired there after abdicating in 1960.

The monarch – dubbed "King Rat" - infamously remained in Belgium after the Germans invaded, despite the government fleeing to Britain.

Leopold III ignored his exiled ministers, visited Adolf Hitler in Germany and sent flowers to the Nazi dictator for his birthday.

Following the war, he was declared unfit to remain on the throne and his brother became regent.

In a referendum, Belgians voted in favour of allowing the controversial king to return home from Switzerland.

After fierce in Belgium protests against his return, Leopold III abdicated in favour of his son.

In 1960, he moved to Argenteuil from the royal palace with his wife Princess Lilian and remained there, out of sight and mind, until his death in 1983.

Princess Lilian died in 2002 and the castle – in need of renovation - passed to the Belgian state.

It was sold for AUD$13 million to a Belgian business tycoon in 2004 who began a series of upgrades to the property.

Local media reported the estate has its own golf course and its gates are engraved with the intertwined L and L representing Leopold and Lilian.