The end of the war found him at the CMB base at Osea Island in Essex, England. He was asked in late 1918 by Sir Mansfield Smith-Cumming, head of the foreign section of the British Secret Intelligence Service, to volunteer for a mission in the Baltic Sea, where CMBs were to be used to ferry British agents back and forth from Bolshevik Russia. The shallow draught and high speed of the CMB made it ideal for landing on enemy occupied shores and making a quick getaway. Agar and his two boats were technically under the command of the Foreign Office (specifically Captain Sir Mansfield Smith-Cumming head of MI6).