One day the van was fine (1.7 KY diesel) had been off for MOT and only came back with one bit of work required

However, when I tried to start her to move her off the drive the starter spun like a crazy thing but did not engage.

I have done the following so far:
1. Checked the voltage getting to the solenoid 11v - Which to me seems fine
2. removed the starter and checked the action - the cog flies up the shaft as you would expect when operating normally
3. hard wired the solenoid into the battery, bypassing the ignition system - it just spun like crazy but did not engage
Is the starter done in or is there something else I should be looking at?
Simon