Sisley Rain Defender Navy Insulated Coat.  Manufacturer tags size state 44 - I would say a UK Small but please see measurements below.
  • Stand up collar with concealed hood, full zip and snap buttons 
  • Multiple pockets
Pit to pit (measured on the back) is approx 22 inches
Arm pit to end of sleeve cuff is approx 18.5 - 19 inches

If you have any questions please ask and thanks for looking!