GBPUSD ORB after a compressed Asia range: my expansion filter

[LondonScalper]

GBPUSD at London open behaves differently depending on what Asia left behind.

When Asia is a compressed range, London often expands. That is when I allow an ORB. When Asia already travelled, London frequently mean-reverts or chops — ORB breakouts there have been expensive noise for me. Compression is not "quiet because I feel bored"; it is width versus recent sessions.

Rule I actually follow: measure Asia high–low before the London cash window. If that width sits in the lower third of the last twenty sessions, ORB is permitted (break plus retest). If Asia width is already large, I switch to pullback or stand-aside — I do not force the breakout costume. UK data into the open cancels the filter entirely; then the stand-aside window owns the morning.

I keep the same stop philosophy either way: other side of the box, no widening because cable "always runs".

• Do you quantify Asia compression before GBP ORB, or is it visual?
• What percentile / lookback do you trust?

Trying to keep this mechanical enough that Monday mood cannot override it.

[PropScalpDesk]

Lower third of twenty sessions is close to what I use. The adjustment I made is for Mondays. Monday's Asia session follows the weekend and can be unusually quiet or distorted by a gap, so it drags the percentile around. I compare Mondays only against earlier Mondays, and I measure Asia as a fixed window, 00:00 to 07:00 London, so that daylight saving changes don't quietly shift what counts as Asia.