Found this in my event log, not sure if thatís when the speed increased but it is 23 hours DSL Uptime in 2 minutes so that would tally.
15:31:08, 27 Sep.
dsl:VDSL link Up: Down Rate=58700Kbps, Up Rate=16767Kbps, SNR Margin Down=0.00dB, SNR Margin Up=6.00dB
BT Infinity 1 - 55/10 sync with approx. 51 down /9 up