Actor Sir Dirk Bogarde took the secrets of his orchid-hunter grandfather's 30-year disappearance to the grave.

Now other members of the family have been trying to find out more. They have placed a headstone on the elusive explorer's Brighton grave to ensure he is not forgotten.

Sunlight cast a spotlight on the inscription of the marble headstone as the Van Den Bogaerde dynasty gathered around the grave of their intrepid ancestor.

Its Latin inscription translated as "man of mystery" and a delicate stem of orchids lay on the grassy mound in Woodvale cemetery, Brighton.

The youngest members of the family played hide-and-seek behind crumbling tombstones as their parents and grandfather Gareth paid tribute to Aime Van Den Bogaerde, whose amazing adventures are still being unravelled 64 years after his death.

On Sunday, English and Belgian members of the family met at his grave to unveil a headstone and toast his memory in champagne.

An integral figure missing from the unusual reunion was Gareth's older brother, Sir Dirk Bogarde - originally named Derek Niven Van Den Bogaerde.

The actor and novelist took many of Aime's secrets with him to the grave in 1999. But he did leave behind some pointers for his family in their quest for the truth.

The future Sir Dirk met the grandfather he never knew he had in 1931. Out of the blue, an intriguing elderly man with epic tales of foreign lands captured Dirk's fertile imagination.

He became a regular visitor to Aime's studios in Ditchling Rise, Brighton, but Dirk's father, Ulric, was discouraging. He never forgave his father for abandoning him and his mother 30 years earlier.

Such was his anger, Ulric forbade mention of Aime's name in his house and his amazing story only survived thanks to the whisperings of Dirk to Gareth and a series of recently unearthed letters and journals.

In 1899, Aime set sail for Baranquilla, Colombia, on board the SS Jamaican to try his luck as an orchid hunter after losing his inheritance.

His wife, Grace, and only son, Ulric, were left to fend for themselves in Birmingham. However, they were never far from his mind and Aime wrote his first letter just after setting sail.

From Baranquilla he travelled by paddle steamer up the Magdalena River to Port Ocana. Here he hired mules and trekked into the mountains in search of the White Cattleya, a rare and valuable orchid much sought after in Europe.

Not long after his arrival, revolution broke out and Aime wrote home about increasingly hairy situations.

In his last letter to Grace he said: "We were shot at nearly the whole time by the revolutionaries and only escaped by a miracle.

"A poor fellow called Lidstone was shot through the arm, two more were shot through the legs and two were killed. We had to leave the poor fellows behind.

"An orchid collector was nearly killed with large knives and I escaped with a bullet through my hat."

He finished by saying he intended to return home, having made his fortune by sending thousands of orchid bulbs to England.

He wrote: "Never to part anymore, duckie, from your loving hubbie, Aime."

This was the last she heard from him. She died in 1917, assuming her husband had been killed in the depths of South America.

Although Gareth knows many of Aime's swashbuckling stories in the Colombian mountains, he was never told where his grandfather had been during his unexplained 30-year absence. Whether Aime ever told his son Ulric and grandson Dirk is unknown.

Gareth said: "Nothing was heard of Aime until 1931 when he telephoned his son, Ulric, who was art editor of The Times.

"Aime said he had followed Ulric's career, about which he was pleased and proud, that he was now living in Brighton, that he was ill and wished for a meeting.

"Ulric, my father, was deeply shocked by this sudden appearance after so many years. When asked about Aime he would only reply 'we do not talk of him'.

"Derek (Dirk) was intrigued by the wild stories his grandfather told of shipwrecks and pirates. My brother never knew whether to believe them. But he never said where Aime disappeared to or why. If he did find out about the lost years, Derek never told anyone. In fact it seems he adopted much the same attitude to his grandfather as his father did and rarely discussed Aime with the rest of the family.

"I think because he was a teenager he had the same ideas as our father. I was only a baby at this point."

Gareth, 68, puts his family's creative streak down to the inspirational hand-me-down stories of his grandfather's strange history.

Dirk was not the only talented family member. Gareth, who lives in London, was a film producer until his retirement and has three sons who have followed in the Van Den Bogaerde family footsteps.

Brock, 43, who lives in Petworth, is a film producer, Rupert, 40, has just written his second highly-acclaimed novel, Daybreak Into Darkness, and Ulric, 32, is also a writer.

Rupert, who lives in Hampshire, is about to begin his third novel dedicated to the travels of Aime.

Gareth said: "We are a creative family. A lot of it comes from my grandfather. He did some marvellous paintings and was a forger to make money when he came back to Brighton.

"He turned out hundreds of paintings and sold them to pubs around the city in exchange for drink.

"I think as a teenager Dirk was inspired by him."

Brock agreed: "Dirk was a great adventurer like Aime. He was a teenager who already had a vivid imagination when he met Aime. Dirk took many of Aime's stories to heart and mirrored them on the big screen."

Just before Dirk died, he gave Gareth a letter from a cousin in Belgium, who was part of the family on Aime's side.

Michel Van Der Haert had written to Dirk to suggest meeting after seeing him on television. Dirk declined saying it was "inappropriate".

However, Gareth thought differently. He immediately contacted his long-lost relative and further small pieces to the puzzle were put in place, thanks to information about Aime's childhood in Flanders.

Gareth said: "My father discouraged the meetings because he had assumed for years that Aime had died. I'm not surprised he was angry.

"My grandfather was deliberately forgotten for years and years. He died in 1938 and my father had him buried here without any headstone.

"My father died in 1972 without ever discussing his Belgian family or his father or his place of burial. We never knew where Aime was buried.

"Last year Aime's certificate of burial came to light among Ulric's papers.

"This certificate had never been seen by the family before and we located his unmarked plot in Brighton."