This is not a reed warbler of any kind - just look at the ridiculously long outermost primary for a start.
Note also the long, strong bill with largely dark lower mandible, grey face hardly showing any supercilium, strong dark grey legs, long tail, dull grey-brown wash allover underparts, very short primary projection, rufous wing panel, and even the habitat (Juncus or Cyperus).
It is a Lesser Swamp Warbler (of the dark subspecies parva).