Once a lamp holder has been closed a tab inside secures it from being unlocked. To unlock the lamp holder pressure needs to be added this tab while simultaniously unscrewing. Any qualified electrician would not have any problems with this. All electrical work in Australia and New Zealand must be done by a qualified electrician.
Help: Unlocking a lamp holder.
E14 thermoplastic lamp holder.
E27 Thermoplastic lamp holder with switch.
E27 Porcelain lamp holder.
E27 Metal lamp holder for lamp shade.
E27 Edison lamp holder.
E14 Porcelain Lampholder.
The metal tab is pushing against the white lines causing it to lock. Adding pressure downwards to the tab means that it can be pushed past.
