Complex sentence: He was posted to 52 OUT, RAF Aston Down for a refresher course on Spitfires and rejoined the squadron on 10 January 1942 but soon afterwards was posted to RAF HQ Mediterranean at Valletta, Malta.
Split into simpler sentences: He was posted to 52 OTU, RAF Aston Down for a refresher course on Spitfires and rejoined the squadron on 10 January 1942. Soon afterwards he was posted to RAF HQ Mediterranean at Valletta, Malta.