On October 30, 1687, Juan Bautista Diamante made his last will and testament before the notary Juan Gómez.   In spite of the generous royal patronage he had once received the playwright died a poor man, with little more to his name than a bed 'of walnut-wood', a chest-of-drawers, some chairs, two small writing desks and other odds and ends 'of little value'.   The signature on the will is weak and shaky, and three days later, on November 2 1687 Diamante departed this life at his house in the Calle de Atocha on the corner of San Pedro.   He had asked to be buried in the church of Nuestra Señora de Monsarrate in the Plaza de Antón Martín, but his brothers laid him to rest beside his father in San Felipe.

Diamante's sole and universal heiress was 'Doña María de Castro y Vargas, mi sobrina'.   The names Castro and Vargas are of course those claimed for Diamante's own mother at the time of his application to join the Order of St John - a claim which we now know to have been fraudulent.   In 1695, at the time of her marriage to Francisco de Soto, and again in 1698 when her first child was born, Diamante's 'niece' was calling herself Doña María de Castro Diamante, daughter of 'Don Juan de Castro Diamante' and 'Doña María de Tapia'.   But by the time of her death in 1706 she had reversed the two surnames - a process begun when her second child was born in 1701.

Cotarelo's suggestion that María Diamante may have been something more than Juan Bautista's 'niece' does seem, on the face of it, sound and we may reasonably conjecture that the 'Don Juan de Castro Diamante' on María's partida is none other than our playwright, Juan Bautista.