Eight persons P, Q, R, S, T, U, V and W are sitting around a square table for dinner in such a way that 4 persons are sitting at the four corners and 4 persons are sitting at the mid-positions on the four sides. All of them are facing the centre of the square. S sits to the immediate left of U. U sits to the immediate left of T. T sits at one of the mid-positions of the sides. R sits third to the right of U. P is an immediate neighbour of both V and R. W is not an immediate neighbour of T. Who among the following is sitting at one of the corners?