due to merging with other ISPs it was giving TalkTalk issues with the other legicey ISPs they had taken on so they just set (mostly) every one to any password so customer could just plug it in and forget (as most users are not techy), it take any username and password or none if the router supports it, so the BT hub would work when the line came back up on TT
i would not recommend the BT hub3 thought (not from my use of it at customers houses, well it works ok in b/g mode with an Fixed channel set like 1, 6 or 11 , N on this router is rubbish a lot of laptops and printers hate the bt hub 3 and 2 in some cases)
like the customer issue i had with one BT infinity setup, they need N mode to get the top end speed but i had to disable the N to get it to work (same issue BT hub3 N tech was making printer and 1 mac and 1 laptop drop from network permanlty untill the hub was rebooted, worked fine in g mode), Thing is when an BT tech remotely logs in when wifi is not working they do the same thing i do to fix it no N and fixed channel