After the March on Rome on 28 October 1922, in which the Fascists took power in Italy, Grandi became part of the new government; first as the undersecretary of the interior (1923), then as the Italian Minister of Foreign Affairs (1929) and then as Italy's ambassador to the United Kingdom (1932 to 1939). Grandi was an ally to the most radical and violent groups of fascists, always surrounding himself with members of the Blackshirts. He used his power base to voice criticism of Mussolini's attempt to reach an armistice with left-wingers and was at one point under suspicion for having attempted to replace the latter with the skeptical alleged Mussolini forerunner Gabriele D'Annunzio.