Re: HSC 2012 Marathon :)
9 must be locked next to 2 and 1.
8 can only go next to 1,2 or 3, but seeing as 1 and 2 are next to 9, 8 must definitely be next to 3, and either 1 or 2.
7 can be next to 1,2,3 or 4. As 1,2,3 are next to 8 and 9, 7 must be next to 4 and either 1,2,3.
From these...