Apple chargers are weird. The mains connector is an IEC C7 / C8 connector, but there is an extra metal tab alongside that can provide ground but does not always

Apple chargers are weird. The mains connector is an IEC C7 / C8 connector, but there is an extra metal tab alongside that can provide ground but does not always. My M1 MacBook Pro came with a UK plug, in which the slot in the top of the plug for the tab is entirely plastic. So, as it came out of the box it is not grounded. I am using a mains extension lead that connects to the charger where the plug goes; its slot has metal connectors on either side that you can see if you look into the slot from the direction that the tab goes in. So, with the extension lead, the charger is grounded. I noticed the mains buzz feeling in the case of my old MacBook when I used an ungrounded charger. I have only used my M1 with the grounded mains extension lead, and there is no tingle.