Result

Thanks to some knowledgeable ringers onTwitter I was given the email address of Morten Helberg who quickly confirmed the details as follows:

 

Date	Place	Coordinates	Observers	Days/km/°
29.04 2013	Østensjøvannet, Oslo, Akershus & Oslo, Norway	59°52'51"N 010°49'57"E	Lome, Carsten Sandøy, John	-
30.04 2013	Østensjøvannet, Oslo, Akershus & Oslo, Norway	59°52'51"N 010°49'57"E	Isaksen, Kjell	1/0/0
14.06 2013	Østensjøvannet, Oslo, Akershus & Oslo, Norway	59°52'51"N 010°49'57"E	Sandøy, John	46/0/0
01.07 2013	Østensjøvannet, Oslo, Akershus & Oslo, Norway	59°52'51"N 010°49'57"E	Evenrud, Jon Johansen, Arnkjell	63/0/0
02.07 2013	Østensjøvannet, Oslo, Akershus & Oslo, Norway	59°52'51"N 010°49'57"E	Mjelde, John Martin	64/0/0
14.12 2013	Druridge Bay Country Park, Northumberland, Great Britain	55°17'38"N 001°34'52"W	Elliott, David	229/897/240

CR-Code White ring with black code: J1TL LBM;RBWN(J1TL)
Ringing Centre Stavanger Museum (Norway) Ring number K03055
Species Black-headed Gull  Larus ridibundus
Sex Male Age 3 cy+

Many Thanks to all involved. It is fantastic when you get such a quick response.