You have to create an app password and use that in TB in place of the webmail password.

https://www.virginmedia.com/help/broadband/manage-email-settings

Looks helpful, I'm amazed that you've found your way through Virgin's tortuous help system. I'll give it a try later - fingers crossed!

The link found by sfhowes to the Virgin Media help site still works, and looks as though should be the answer, BUT Virgin have clearly changed things (as always) and the current help article makes no mention of "app passwords", and I can't find anywhere in the present Virgin Media account management system that offers "Generate new App password". Any other suggestions? 10

There's a section on the page cited above:

"How to set an app password to use an email app"

It refers to phone apps, but in the next section it's stated that an app password is needed for 'another email app'.

Thanks so much for looking into this for me. Yes, but what is meant by an "app password", and how do I create one, as it no longer seems to be an option on the Virgin website?

From https://www.virginmedia.com/help/broadband/manage-email-settings

"How to set an app password to use an email app

To set up Virgin Media email on an android or iPhone email app, you need to create a separate app password through Account settings on the My Virgin Media app.

To get the password, follow these steps:

Sign in to My Virgin Media on the app

Go to Account settings, then Account details.

Under Virgin Media Mail, tap Manage next to Manage your Virgin Media Mail app password.

Under Virgin Media Mail app password, tap Generate new App password and follow the instructions.

A new secure app password will be generated for you, you can use it in all apps that access your Virgin Media mail address. If you create a new app password, you’ll need to update all your existing apps with the new password.

Your separate app password will help make things more secure as IMAP and POP don’t use extra protection like Multi Factor Authentication.

Remember that this password is separate from your sign in details for My Virgin Media (or any Virgin Media apps). So, if you need to check your Virgin Media Mail emails through My Virgin Media or at mail.virginmedia.com, you'll still use your My Virgin Media password."

Since I don't have a Virginmedia account, I cannot confirm this.

Fantastic! I trawled through the Virgin Media setup procedure for the nth time and finally found the app password! I can now access my blueyonder emails again. Very many thanks.