Giovanni Francesco Romanelli

Giovanni Francesco Romanelli came from Viterbo, north of Rome, and learned his trade assisting Pietro da Cortona, the leading decorator of Barberini Rome, on the palace of the pope's family from 1631. Master and pupil later fell out, and Romanelli made his own way with Barberini backing. In 1639 he was elected head of the Accademia di San Luca, the painters' academy of Rome.

His widest fame came in France. Cardinal Mazarin, the chief minister, called him to Paris in 1646 to paint the gallery of his palace, and in 1655 he returned to decorate four rooms of the summer apartment of the queen mother, Anne of Austria, in the Louvre, whose ceilings still survive.

The Sibyl at the Galleria Borghese is a smaller, quieter picture, a prophetess in a turban-like headdress who looks upward as she writes down one of her obscure prophecies. It reached the Borghese late, probably bought by Prince Camillo in 1818 or 1819, and in the 19th century it was listed as by Guido Cagnacci, a painter from Romagna. Hermann Voss gave it to Romanelli in 1924, and no one has disputed it since. Romanelli died in Viterbo in 1662.