Pound rallied against US dollar on Frankfurt open. This is often the case when 6:00 GMT hits the clock. However, Frankfurt rallies are often known as Frankfurt fake outs. If you look at gbp/usd chart below you will see that reversal candle is also in formation.
London open is due in 10 minutes and breakout may turn to be real. However, we need to see a push through 1.5700 level in order for a breakout to be confirmed. I would personally wait either for a reversal sign or for a continuation pattern set up.
Stop loss orders should be tight. There is no major news that may rock the market, so if the move is real it will continue running on expectations for a rate hike from BOE in the nearest foreseeable future.
Possible Frankfurt fake out on 15 minute chart in gbp/usd