Does the first M5 candle at 08:00 say anything about the day?

[FXS London Scalper]

It's often said that the first five-minute candle of London sets the tone. That's easy to test on EURUSD with a year of M5 data.

Method: compare the direction of the 08:00 to 08:05 candle with the direction of the 12:00 close relative to 08:00. Count matches.

How to judge the result. With 200 days, a 54% match rate (108 days) is about one standard deviation above 50%, well within what chance produces. Restricting to large candles, say over 8 pips, may push the rate higher, but a subset of around 60 days needs a match rate in the mid-60s before it means much.

So the likely answer is a slight edge at best, not enough as a directional bias alone.

A more specific pattern is worth testing alongside it: a large first candle followed by a second candle that retraces less than half of it. The idea is that shallow retracement shows the opening move has support, which should make follow-through in the next 30 minutes more likely. Test it the same way, against all large first candles, not just the ones you remember.

A short Python script on exported M5 bars does all of this. Has anyone run it on GBPUSD?