GBPUSD broke below 1.6430 support, suggesting that the upward movement from 1.6219 had completed at 1.6593 already. Deeper decline would likely be seen over the next several days, and the target would be at the lower line of the price channel on 4-hour chart. Resistance is at 1.6593, only break above this level could trigger another rise towards 1.7000.
