It may be the light, but this bird appears to have pink feet.
No interactions present.
This is a tricky photo of a sub-adult bird with some contrasting features - the mantle points to lesser, but the legs are distinctly pink....bill sizes does not seem massive enough for greater, but it may be one of those photos best left at genus.
Lat/Lng: 51.5027, -0.0273
OS grid ref: TQ370800
On the river, not far from the Hilton-Canary Wharf Ferry landing.