Albert-Marie Edmond Guérisse was born in Brussels, Belgium where he studied medicine in Brussels University before he joined the Belgian army. At the outbreak of War, Guérisse enlisted as a Medecin-Capitaine in a Belgian cavalry regiment. After Belgium was forced to surrender, he escaped to Britain through Dunkirk and enlisted in the Royal Navy with the name Patrick Albert O'Leary, a name of a Canadian friend. He joined the crew of a French ship that had been renamed HMS Fidelity.
During an April 25 1941 mission to place SOE agents in Colliore, Belgium, Guerissa was in the skiff on its way back to the ship when it turned over and he had to swim ashore. To the Vichy French coast guards, Guérisse claimed he was a Canadian airman Pat O'Leary and he was taken to St. Hippolyte Fort near Nimes. There, he met British officers and SOE operative Ian Garrow got him released then and took him to Marseille. Guérisse proceeded to help Garrow run his escape network and continued to use the O'Leary moniker.
When Vichy France authorities captured Garrow in October 1941, Guérisse took over. He smuggled a German uniform to Garrow in his cell in Mauzac concentration camp and Garrow used it to escape on December 6. The British demanded that Garrow should be returned to London. Guérisse continued his work, expanding the escape line's operations. The line carried over 600 escapees to Spain and back to Britain.
In January 1943 the escape line was infiltrated and betrayed by French turncoat Roger Le Neveu and Guérisse was arrested in Toulouse in March. He managed to get one of the younger members, Fabien de Cortes, to flee the train when they were transported to prison to warn the British.
Guérisse told nothing to Gestapo interrogators when he was tortured and then was sent to a series of concentration camps. In the summer of 1944 he was at the Natzweiler-Struthof concentration camp in Alsace with SOE agent Brian Stonehouse. At the camp he witnessed the arrival of four other female SOE agents, Andrée Borrel, Vera Leigh, Diana Rowden and Sonia Olschanesky who were all executed and disposed of in the crematorium in an attempt to make them disappear without a trace. After the war, Albert Guérisse and Brian Stonehouse were able to testify at the Nazi war crimes trials as to the women's fate.
Finally, Albert Guérisse was taken to Dachau, tortured again and then sentenced to death. However, when SS guards surrendered before the Allied advance, "O'Leary" took command and refused to leave before Allies agreed to take care of the inmates.
After the War, Guérisse took back his own name and rejoined the Belgian army. In 1946 he received a George Cross. In 1947 he married Sylvia Cooper-Smith. He served in the Korean War where he was wounded trying to rescue a wounded soldier. He received 35 decorations from various countries, including honorary Knighthood and title of a Belgian count. He became the head of the medical service of the Belgian army and retired in 1970 with the rank of major general.