By Henri Astier BBC News Online

Twelve suspected mercenaries are back in France, after their plane was intercepted in Tanzania on its way to Madagascar.

The men - all believed to be French nationals - walked away free after their aircraft, which had been expected in Paris, landed in Lyon.

Mercenaries have roamed France's former colonies since the 1960s.

A former French foreign minister - Louis de Guiringaud - said in 1977 that Africa was the only continent where France could still "change the course of history with a few hundred men".

Traditionally Paris has used regular troops to shore up friendly regimes. But French governments have also turned to "dogs of war" - as mercenaries are commonly known.

White mischief

Foremost among them was the legendary Bob Denard.

Denard headed President Abdallah's presidential guard

He began his career in the 1960s in what was then the Belgian Congo.

Denard was later active in Nigeria and Angola, and is thought to have been involved in at least four coups in the Comoro islands.

But by the 1990s, France - at least officially - focused on making history by supporting democracy, rather than dubious clients, in Africa.

The French became more reluctant to intervene militarily - especially after its operation in Rwanda in 1994, which cynics said provided an escape route for those involved in the genocide.

This meant that Paris no longer routinely hired mercenaries to do its dirty work.

Not out

In retrospect, the mercenaries' glory days came to an end in 1995, when French troops quashed Bob Denard's final coup attempt in the Comoros.

In 1999, Denard - then 70 - was tried in connection with the assassination of President President Ahmed Abdallah ten years earlier. He was cleared.

France's dogs of war are down, but they are not out.

French pilots were used during the civil war in Sierra Leone - although they seem to have been in it only for the money.

The latest incident involving Madagascar suggests that French mercenaries may have lost official backing - but they're still active.