Six officers, P, Q, R, S, T and U, have offices in a row along a corridor, numbered 1 to 6 from left to right, all facing the same direction. The following facts are known:

1. Q's office is at position 3.

2. R's office is immediately to the right of Q's office.

3. P's office is at one end of the row.

4. T's office is not adjacent to Q's office or R's office.

5. S's office is second from the right end.

6. U's office is adjacent to P's office.

Who are U's immediate neighbours?