Hi Ziaul,
Yes, that has fixed it thank you! The reason I did a restore from backup was that the previous fix, although it seemed initially fine on checking it, unfortunately it didn't last. I didn't get back to work on the site until several days later and although I didn't have the 404 error, the link returned a page but without the actual article included. Hence the restore, but my backup only included the database issue and not the 404 error issue. Thanks so much again for the support.
Regards,
Linda