What might change that or make it stronger?

The GBPUSD fell on the back of the ECB decision yesterday. It was more a reaction to the EURUSD's fall. That fall took the price right to 100 bar MA on the 4-hour chart. The 200 hour MA was also in the vicinity and the 38.2% of the move up from the Feb 29th low. Since then - with the help of the EURUSD surge perhaps - the pair has pushed back higher.

Now the pairs rally yesterday hit the topside trend line (point 3 in the chart above) and came back down. That is a ceiling and level that the pair needs to get to and through to continue the upside momentum.

The correction today, came down toward the 50% midpoint of the move down from the February 4th high at 1.42509 and the broken trend line coming from that same high. That correction held the level. That give me the more bullish feelings. Stay above is bullish for the pair going forward.

The topside trend line target comes in at 1.4325. Above that the 1.4349 and 1.4366 are other targets.

PS if the EURGBP has helped shape the EURUSD, the pair also has been an impact on the GBPUSD. The EURGBPs fall has hurt the EURUSD but also kept the GBPUSD steedy. The 38.2% held resistance on the last correction (see chart below). But there is lots of support at the 0.7750 area.