He earned notoriety at an early age by telling Napoleon to his face at the conference in Bayonne in 1808 that the Portuguese would not ‘consent to become Spaniards’ as the French Emperor wanted.

The resulting document, to which the King was unable to agree, was so liberal that it drew down on Palmela the hatred of the reactionary forces in the country, especially the Queen and the Infant Dom Miguel, who in 1824 had him arrested.

Greville noted in his diary for 16 August 1828:[1] ”Esterhazy told me to-night that Palmella entertains from twenty to thirty of his countrymen at dinner every day, of whom there are several hundred in London, of the best families, totally destitute.”Miguel condemned him to death in absentia and seized his estates, but Dom Pedro, Emperor of Brazil, appointed Palmela guardian to his daughter, the rightful Queen Maria II, and he acted as her ambassador at the British court.

In 1830 he set up the young queen’s regency on Terceira in the Azores; it was at this time that he became acquainted with Captain Charles Napier whom he considered the best person to command the Liberals' navy.

He served briefly Prime Minister again in February 1842 (for two days, in the so-called Shrovetide Cabinet), and from March to October 1846 (during the height of the Revolution of Maria da Fonte).