Originally formed as a Royal Naval Air Service unit in Feb 1914, it was numbered 3 Squadron, RNAS on 26 Feb 1915 and redesignated 203 Squadron when the RAF was created on 1 Apr 1918. Associated with the Middle East and East Africa until after World War II, it was disbanded as a Nimrod maritime reconnaisance unit at RAF Luqa (LMML) on 31 Dec 1977. Its association with helicopters began in Oct 1996, when the Sea King Operational Conversion Unit (OCU) at RAF St Mawgan (EGDG) in Cornwall was redesignated 203(R) Squadron as a reserve unit. In early 2004, it flew the Sea King HAR.3A. 
203(R) Squadron provided vital, temporary SAR cover for Cyprus from RAF Akrotiri (LCRA) between Jan and Apr 2003, while 84 Squadron was working up with its Griffin HAR.2s in the UK (having by then relinquished its Wessex HC.2s). In anticipation of the RAF St Mawgan hand over to civil operations, 203(R) Squadron started preparations in May 2008 and in Aug 2008 moved its Sea Kings to RAF Valley.
Last OCUs Sea King course graduated on October 8, 2014
1930, based at Basra in Southern Iraq flying Supermarine Southamton Sea Planes Twin engined, wooden hulled, biplane Flying boat. Photgraph of serial number S-1152 moored on the River Euphrates from Derek Payne
Locations | |
| Years | Location | ICAO/FAA |
| 2008/14 | RAF Valley | EGOV |
| 2003 |  RAF Akrotiri | LCRA |
| 1996/08 | Newquay / St Mawgan  | EGHQ |
Models | Login to Edit | |
| Years | Models | |
| 1996/14 | Sea King  | |
203(R) Squadron List of helicopters | Help Us | |
| C/N | Version | Built | In this Org | In other Org | |||
| wa 855 | har.3 | 1978 | XZ589 : pictured (pic2) as /E 203 Sqd(R) at RAF St Mawgan Families Day | |||
| wa 859 | har.3 | 1978 | XZ593 : RAF;24/25jul99 203Sqn. Fairford air show : HAR.3 203 Sq by Aug 1999 | |||
| wa 865  | har.3 | 1978 | XZ599 : 02 pictured (pic3) with 203 Sqd at RAF St Mawgan Families Day |  XZ599 | ||
| wa 886 | har.3 | 1980 | ZA105 : picture with 203 Sqn at RIAT air show, UK | |||
| wa 947 | har.3 | 1985 | ZE368 : RAF; 24+25jul99 203Sqn. Fairford air show : HAR.3 203 Sq by Aug 1999 | - ZE368 | |||
Operations | |
| Dates | Operation | |
| 16-aug-04 | 16-aug-04 | Boscastle Flood Disaster |