What's happened to my latency? Plusnet network is going backwards

[#1]

I' running the Thinkbroadband Broadband Quality Monitor.
Something happened to my connection today just after 4pm when the minimum latency jumped by about 3ms.

I'm seeing an increase of about 3ms when pinging ntp.plus.net over the times I've always seen.
I also have f8lure running which shows a similar picture (see attached) which shows a similar increase just after 4pm. Between 9:30 and 10 pm I was gateway hopping which explains the other lines on the graph. This shows that the increase is not gateway dependant.
I've checked my router log and there was no reconnection around 4pm.

[#2]

Normal pings have not come back overnight:

[#3]

I've seen the same thing since I set my monitor up, I assumed it to be normal and a product of it being peak time. My performance and ping times at home certainly don't seem to be affected although I don't do a great deal of gaming (haven't done any this week).

[#4]

Bob, It's staying at that higher level 24hours a day across all the gateways I've tried so it's not a feature of peak time. It's something either Plusnet or BT have changed.

[#5]

Quote from: jelv

It's something either Plusnet or BT have changed.

Are you sure it's not been like this for a while? My monitoring has only been set up since the 29th Jan however every day has exhibited the same symptoms with the exception of last Saturday (connected via various gateways during that time).
I have spoken to Dave about this this and it's something we're looking into as it does seem peculiar. We also set up some additional graphing yesterday afternoon which should hopefully help us see what's going on.

[#6]

Looking at earlier graphs Monday has another step change in the other direction - but not from as a high a level as it has gone to now.
Here's all the graphs to date since I activated the monitor (I wonder if TBB would release the raw data to you if I gave permission?).
Friday 29/01:

Saturday 30/01:

Sunday 31/01:

Monday 01/02 (the red bar is where I turned off ping responses in my router for a short time to see how it showed up in the graph) :

Tuesday 02/02:

Wednesday 03/02:

Thursday 04/02:

Friday 05/02 (today so far):

[#7]

Just seen your post here although I can see the latency increases from before Wednesday.

[#8]

You should be able to see the complete set now. If you look at my connection logs you'll find I've been bouncing around a bit.
Would you like me to try disabling pings for about 10 minutes again to see if it induces another change (the router invokes a reconnection when I change this).
Also I'd be happy to try with a different log in to see if that affects things - I'd have to set up another tbb monitor for the changed IP.