can anyone tell me if the attached photo is a gas bayonet fitting which is attached to my mom's cooker and can I disconnect this myself without employing a gas safe engineer ?
That is a gas bayonet fitting - B554 1/2” Straight Bayonet. It seals off the gas when it's removed. EDIT: http://www.bowbros.co.uk/page5a.html
Will you be fitting a new replacement cooker?, if not then the best bet would be to employ a GS person to remove the bayonet connector and plug the elbow, making sure that after it is gas tight. Although the bayonet connector does have a safety feature (a spring return valve) which will shut of the gas, once the hose has been removed, it should not be relied upon. I have seen one fail when having a check done, after leak detector spray was sprayed around the connector. And this was a relativity new part. If a new cooker is to be fitted, then it may be a good idea to replace the connector for a wall plate, as it doesn't seem to be fixed to the wall? Just make sure there is no cables behind the wall as there appears to be a socket in the vicinity.
Thanks both. I had hoped to remove the cooker and simply switch the gas off at the mains as the property will be vacant for a while