Triggering capital loss on shares

Client company is insolvent.  The company is not yet in liquidation but soon will be.  He has shares he paid £50k for and a Director's Loan Account balance of £45K.  It is unlikely he will get anything back out of the company as secured creditors and very little in assets.  At what point can he claim a capital loss on the shares and DLA?  Is it feasible for this claim to be made in 2011/2012 if the company was declared insolvent (which it was) before 5/4/2012?

thanks for your assistance.