Technical Hose fitting removal

[imported_woolfie]

Hi troops . Can you advise how I can remove the white fuel connection from the elbow . I need to replace the o ring but need to take elbow I to work to get an appropriate size o ring

 

[ZaphodB]

Looks to me like the off-white collar slides up or down to release a lock?, but make sure any pressure in the pipework is released first , and might need some of the crud cleaning off first too