The 9 combinations that exist for two movements:
R,R
R,L
R,U *
L,R
L,L
L,U
U,R *
U,L
U,U
Walker would only be able to make it to (1,1) with only 2 of these combinations.
So if he were only allowed to make two movements, his chances of arriving at (1,1) would be 2/9.