BT socket spur/microfilter confusion

[Dfbrand]

Hello all, long time peruser, first time user. I've had a botched BT install and I've had an engineer back to fix it today. I have a question and he wasn't sure. I've attached a picture for clarity.
So the socket was replaced today, the black cable on the right goes to a phone upstairs. It used to plug into the socket but he has now wired it to come directly off the socket (it goes in underneath).
The cable plugged in is an extension, into the end of it is an ADSL filter and into the filter is plugged my BT router.

My question is... as the phone upstairs is now connected directly to the socket, is it going to cause problems with the ADSL? As to be it appears that the spur going off upstairs doesn't go through a filter.

Hope this makes some sense. If you need a diagram let me know and I'll knock one up.

Thanks for your help all!

[Dfbrand]

Ive added a very crude diagram just for clarification (or possibly further confusion...)

[BenMcr]

It's been a very long time since I've had BT based broadband, but I'm pretty sure you need a microfilter on all sockets that have a device plugged into them.

[pip08456]

With the socket you have you will need filters for any phones you wish to connect.

As the engineer has fitted a "new" socket I would've expected him to fit one with a SSFP which would negate the need for filters.

[jb66]

The new 5C master socket doesnt seem to have a adsl filter built in so you will need one for your phone upstairs

[Dfbrand]

Unfortunately he didn't fit one of the filtered sockets, that would have been nice....

Thanks for your answers all, so I'm guessing that as long as a filter is plugged in at the end of the spur upstairs then there shouldn't be a problem? I was just concerned because I was always under the impression that the micro filter had to be the very first thing off a socket and I wasn't sure whether this spur would 'precede' the main connection off the socket. Do I make any sense?

Thanks again!