Ignore!
Although Myrtle Lloyd is the Director General of Customer Services for HMRC, I feel sure that emails from HMRC don't go out under her name. It's almost certainly linked to some sort of scam.
Check the 'extended headers' for the email you've received. The way to view them varies between different email systems but, as an example, I need to click on the little 'i' (for 'information') icon next to the date at the top of an email, such as this one which
appears to come from HMRC:
https://i.postimg.cc/ydbC2Q84/EM3.jpg
Doing so takes me to a detailed sheet of information, with the top bit looking like this:
https://i.postimg.cc/4xgy8d0v/EM4.jpg
There you can see repeated references to 'hmrc.gov.uk', proving that the email is authentic and really does come from HMRC. I wouldn't be at all surprised if you see something completely different (such as a gmail address, for example) if you check the extended headers on your 'HMRC' email.
If the headers don't look right, it's a scam. If the headers you see are genuine, you can probably still ignore the email unless it clearly needs some sort of action.
[Note: With some email systems you need to go to 'Properties' in order to find the option to 'view extended headers'. The only PC email client I know of which doesn't let you view extended headers is the (dreaded) Windows Mail app. If you're using that to view your email, you'd need to access your mail via your email provider's website instead to be able to see them]