An investor agreed to subscribe to new shares in a my company. He
agreed to put in $2M for 50% of the company (i.e. he valued the
company at $2M pre-money). Some months later, he changed his mind. The
company could not find another investor but an independent consultant
valued the company at $1M at the time of the breach.

The company intends to sue the first investor for breach of contract
but I need to know how much damages we can get if we succeeed in our
action before we proceed.

Are we able to claim $2M if we succeed? Can the investor claim that
there is no loss because we did not have to issue any new shares? How
should the damages be computed?

I am looking for some authority/past legal cases preferably in UK or Australia.