If you read the KCSIE March 2016 ( look out for the new edition in September ) then the topics a DSL needs to know all about include : E safety, FGM, CSE, Domestic Abuse, Prevent and radicalisation, Mental health ( including self harm) and the areas of abuse, Physical, Emotional, Neglect and Sexual. Not only do we need to be aware of the issues, we need to consider how we are training our pupils and staff, so PSHE and support ( counselling for example) is also relevant.
This list is a working progress but here are some of the great people on Twitter who a DSL should have a look at:
Education / training
If you know of anyone else please do comment.