Original: A Lance-Sergeant in the Guards and Honourable Artillery Company wears three chevrons, belongs to the Sergeants' Mess, and is considered senior to "normal" Corporals; however, for practical purposes he remains a Corporal rather than an acting Sergeant (e.g., he will typically command a section).
Simplified: A Lance-Sergeant in the Guards and Honourable Artillery Company wears three chevrons, and is considered senior or higher up to "normal" Corporals. For most purposes, he still remains a Corporal rather than an acting Sergeant (e.g., he will typically command a section).