He embarked on several expeditions with Edmund Hillary: the 1956-58 Commonwealth Trans-Antarctic Expedition to the South Pole on which he served as radio operator; the 1960-61 Silver Hut expedition, a scientific and mountaineering expedition (plus Yeti hunt) to the Himalayas, on which he suffered pulmonary edema at on Makalu. Mulgrew had to be carried part-way by a Sherpa (Urkien). He was an appalling sight and it was a miracle he was still alive. A helicopter took him from the Barun Valley () to Shanta Bhawan Hospitlal in Khatmandu. Hilary was horrified when he saw him and got his wife June to fly to Nepal. In New Zealand both frostbitten feet were amputated.