50% and the 100 bar MA on the 4-hour comes in at 1.4007-11
The GBPUSD moved to a new session low at 1.40174. In the process, the pair is getting closer to a cluster of support defined by the 50% retracement of the move up from the March low at 1.4011 and the 100 bar MA on the 4-hour at 1.40077. That natural level at 1.4000 is also in play.
A break below each of those levels, increases the bearish bias for the pair.
The pair fell below the 200 hour MA and a trend line yesterday. That was a catalyst for more bearish bias since then (green line in the chart above currently at 1.41084).
On a rebound, the close resistance comes in at the early London/European lows at 1.4035. Stay below is more bearish. A move above will lessen some of the bearishness from the break lower. Remember it is month/quarter end.