Sorry gentlemen yes the test socket is the back most socket. Thank you for your guidance. I have been lead up the garden path by the overseas call centres when conducting test last year as I was never asked to remove the “I – Plate filter “. Not used to this newfangled stuff had a 40 year old phone socket with twin figure of eight grey drop wire only replace 18 months ago which is when the MK3 Master Socket was fitted. More alarming than I thought not only responsible for internal wiring but MK 4 faceplate filter, phone leads, phones, RJ11 lead, and Smart Hub having to have an inline plug in filter that works, definitely have to fear next engineers visit. Have to consider if it is worth having Broadband at all. Especially when the engineers say the cabling in my area is poor so will always have problems 21Mbps speed loss in 700M due Cross Talk and poor cabling acording to engineers.