Alex Kidson (op. cit.) notes that although this portrait is dated 1780, it was actually painted from seven sittings between 1777-8 (according to the sitter book) with Romney receiving payment from Mr Bertie in April 1778. Kidson queries the traditional identification of the sitter on account of the sitter looking younger than 68 years old and also due to the fact that the sittings in 1778 were recorded under the name Colonel Bertie. One possible explanation is that Peregrine Bertie’s son, Colonel Bertie, accompanied him to his last sittings and made the appointments on his behalf. Alternatively, it is conceivable that the seven sittings do not all relate to this portrait. Romney also painted a portrait of Colonel Bertie (sold at Christie's, London, 3 December 2014, lot 181), as a companion piece to this portrait, which the artist began in 1778 and took 8 years to complete.