Nothing given!? Theo Walcott (Arsenal) was clearly brought down in the box by Willian (Chelsea)

At 0-0 in a tense first half between Arsenal and Chelsea, a contentious incident occurred.

Theo Walcott received the ball from Mesut Ozil in the Chelsea penalty area.

Walcott went down under a clumsy challenge by Chelsea Brazilian midfielder Willian.

The referee, Mike Dean saw nothing untoward but surely there was contact?