My "Superfast" fibre has suddenly halved in speed since switching to Sky Mobile

[No2ID]

I have superfast FTTC.  For years my router has been syncing at 79988/19999 but in the last 2 days it has gone to syncing at 45231/18999.  I used to get 72Mbits download; now I get 42Mbps.  The weird thing is that this drop in speed EXACTLY corresponds to my switching to Sky Mobile 2 days ago.  What possible connection could there be between them?  But the correlation is just too perfect to be coincidence.

Obviously I am going to complain to Sky but has anyone else seen such a thing?

************* UPDATE: on rebooting the router it has returned to the maximum sync speed and download speeds are restored.  Still really really strange though 

[Chrisee]

@No2ID Glad you sorted your issue but I can reassure everyone there is zero connection between buying Sky Mobile and your Broadband speeds so coincidence is the only explanation.

The two systems are technically totally independent your mobile coverage uses the O2 network and your broadband uses the Openreach network.