After touching the downward trend line on 4-hour chart, GBPUSD dropped down from 1.6643, indicating that the pair remains in downtrend from 1.7190. Deeper decline to test 1.6536 support would likely be seen, a breakdown below this level will signal resumption of the downtrend, then next target would be at 1.6400 area. Resistance is now at 1.6643, only break above this level will signal completion of the downtrend, then the following upward movement could bring price back to 1.6800 area.