Basil’s father was Basilius Petrides who had Greek Ancestry (his relatives originated from the Island of Symi) and was educated at Dulwich College in England, the same school that Basil attended. He was a businessman who worked in Nicosia, Cyprus before retiring to run a small holding in East Sussex, England. Basil Petrides initially joined the RAF as a Sgt and served a tour of duty with No.50 Squadron, at RAF Waddington, as a Wireless Operator – Airplane Gunner (WoAG) in Handley Page HP.52 Hampden twin-engine bombers. He flew his first mission, a mine-dropping mission known as “Gardening” in RAF slang, during the night between 18/19 May 1941, joining P/O Abbot's crew manning the AD.852. He flew his second operational sortie 13 days later, on 2/3 June, targeting Dusseldorf. The bomber reached its target and dropped the bombs from 13,000 ft with poor visibility. The flak was heavy and accurate, and shrapnel destroyed the centre panel of the pilot’s windscreen. Petrides and the rest of the crew were lucky this time and headed for their base, landing almost 7 hours after their takeoff. Basil flew 17 more missions till the end of August, flying with various bombers and occasionally with different crews. On 27 August 1941 Basil and his crew were scheduled for a bombing mission, flying the Hampden X.2991 but they crashed on take-off, however without anyone injured. It was a close call considering that the bomber was fully armed with bombs. Meanwhile, the No.50 Squadron had already moved to Swinderby on the 19th of July 1941. September was going to be quite intense for Basil. The month began with a Gardening mission during the night between 6/7 September 1941 and one day later he flew a bombing sortie against Kassel, attached to P/O Smith's crew. Despite excellent weather conditions with no clouds, good visibility, and a bright moon, the primary target was not found. On E.T.A. a large town was found on the side of a river believed to have been Hersfeld. After dropping bombs from 2,000 ft, the railway lines and sidings were machined gunned by Sgt Petrides and Sgt. Hudson inflicting further damage. The opposition was very little, and the bomber escaped back to England. Two nights later, on 12/13 September 1941, the same crew were lucky. The target was Frankfurt. The weather conditions were a little cloudy with moderate visibility over the target area. A gliding attack was made from 11,000 ft to 5,000 ft, with bombs being seen to burst, however, one bomb failed to drop. The aircraft was caught on a cone of 40 searchlights and all types of flak shot up against Hampden AE.251, but it managed to get out intact.

Petrides left from the squadron flying schedule for almost a month, probably enjoying a well deserved leave, after 21 missions. He came back to Waddington and flew again on 12/13 October 1941, in Squadron Leader's Potts crew in AE.306 for a bombing mission against a Synthetic Fuel Factory in Huls. Their aircraft dived on target but was caught in the searchlights, and the flak opened up. They released the bombs from 2,200 ft and while taking evasive action they took a hit which was heard as a sharp crack. Several minor hits were sustained but the airplane and its crew escaped unscratched. Basil Petrides flew 7 more missions before his tour ended. During his last sortie, he was flying with P/O Smith crew in P.2094. The mission was to intrude on the searchlight belt and bomb targets in Belgium. They successfully did this and they dropped their bombs near Maastricht while Sgt. Petrides and Sgt. Petterson machine gunned searchlight effectively. On their return journey, the aircraft was hit over Antwerp, and the port engine and petrol tanks were holed.  For his actions with the No.50 Squadron was awarded the Distinguished Flying Medal (DFM) for his bravery/professionalism on this tour. His citation stated at the time:

"This airman has displayed outstanding ability as a WoAG throughout the many sorties in which he has participated. One night in September 1940, Sergeant Petrides machine-gunned trucks and wagons in a railway siding and set two of them on fire, On another occasion in November he used his guns with such good effect that he extinguished six searchlights. This airman has not had a wireless failure in any operation in which he has been engaged. He has shown great keenness and set a fine example".

His award was reported in The London Gazette on 10th February 1942.