Crack at base of outside wall

Just been clearing out our side passage that was a real mess and came across this crack between the path and the wall:

http://i52.tinypic.com/2gsk5kp.jpg

Seems to be evidence of some rising damp as well. What's the best
way of repairing this. I was going to simply fill it in with some
mortar/concrete but on second thoughts reckoned I should ask someone
who knows what they are doing first

Hmm nice damp proof course...! Not

Looks like someone's attempt to create one, or cover one up.

If that motar wasn't waterproofed, it will make it worse.

Hack the plinth off it's of no use cracked.