long exposure light leak?

[MattKHardy]

Hi,

Been trying some long exposure photography in the mornings. Exposure time 5 minutes, 2-stop centre filter, polariser and 3-stop hard grad.

Nearly every shot is showing some sort of light leak coming from the top of the shot. The strongest band of light that leaks in from the top is in the same place every time.



I have changed film holders but the result is the same.

Could this be due to stacking the polariser and grad? Could it be a leak from somewhere else?

Many thanks for any help!