@Rufus+,
If you have forwarded from your TalkTalk email account, then, in your internet browser, log in to the account, click on the gear wheel (top right), click on 'All settings ...', scroll down to Rules, click on the right arrow, and remove the corresponding rule.
If you have imported TalkTalk email in your Google account, then, in your internet browser, log in to your Google account, click on the gear wheel (top right), click on 'See all settings', select the 'Accounts and Import' tab, and remove the TalkTalk account in the 'Import mail and contacts' section.
