Many thanks for your reply.
Yes, the evidence comes solely from my wife who relayed her accusations verbally to her executors before she died,
The paper trail as such is the mortgage application and an extension to that which the prosecution are claiming (with the testimony of an expert), were copied from my wife's driving licence.
In this regard, I gave my wife both these documents which were signed by her in my absence and without witnesses so I have no idea what she used to sign them with.
That's very helpful indeed. Many thanks for your advice.