Rafa Nadal adjusted his cranial-mounted visual apparatus and focused on Andy Murray's socks. Their condition was sub-optimal.

"Your. Socks. Are. No. Longer. < font color="#ffffff" >", he said in disapproval.

"Och," Andy Murray responded. "It's. Just. A. Wee. Bit. Of Grime. Hoots. Mon."

Rafa found his suspicion sub-routines working so hard that he had to run his cooling system at a higher rate to compensate. He would, he decided, hack the socks later and analyse them thoroughly.

The grime appeared to be machine oil.