“Deo Juvante” motto
“With the help of God” was the expression Lambert Grimaldi (the man to whom the inhabitants of the lordships of Monaco, Menton and Roquebrune took a vow of loyalty the day after a dark plot was hatched by his mother-in-law, Pomeline Fregose, in 1458) used in his correspondence. Lambert foiled the plot and secured the fidelity of the inhabitants.
The motto is an eminent feature on the coat of arms and on coins.
Prince’s Family coat of arms