According to Félix Bellamy there were originally two gallery graves; of these one, already in ruins, called the Tombeau de Merlin (the second was designated as the Tomb of Viviane) was the subject of a detailed description in the 1920s.

[2] The Tombeau Merlin is listed on the Base Mérimée, the official French inventory of notable architecture and archaeological monuments.

[6] In 1825, the writer Blanchard de la Musse [fr] associated a gallery grave in the north of the Forest of Paimpont with the tomb of Merlin.

[4] His research, based on Poignand's article and the statements of the inhabitants, led him to settle on this gallery grave as the location of the tomb.

In the 1970s, the Breton writer Yann Brekilien opposed the construction of access roads and the loss of the legendary character of Paimpont-Brocéliande.

It was not until the 1990s that a promotion policy was put in place thanks to the mayor of Ploërmel and the Centre de l'Imaginaire Arthurien, allowing guided tours and the establishment of a protective perimeter around the tomb of Merlin.