They did the same thing yesterday
If you recall, the GBPUSD tested resistance area (actually went a little above) at the London fixing. Today, traders are doing the same thing at the 1.5085-89 area.
The 1.5085 is the 61.8% of the years range. The 1.5086 is the low from May, the 1.5089 is the 50% correction of the trend move lower on the back of the NFP report (see chart below). Yesterday, the price rolled over. Today is different, but the price has dipped back down to 1.5075 initially.
Overall, however, the follow through selling in pairs like the GBPUSD and the EURUSD is a bit disappointing (although resistance is holding) since the initial fall. There has not really been an urgency to sell the GBPUSD. The rise has meandered higher, but the selling is limited.