Hi Les,
This does not really sound like fraud. It does appear to be mismanagement (or "maladministration") of the estate. The executor owes a fiduciary duty to all beneficiaries under the will to deal with the estate assets properly and according to will instructions. If the executor acts contrary to the interests of the beneficiaries (e.g. for personal gain), then there is an action in breach of fiduciary duty and if proved, the executor will be personally liable to make good the amount lost or account for any gains/profits made or tracing could be done to recover the lost amount.
If judgment is made, an enforcement order can be sought and there will be ways to recover the amount: e.g. in one go, periodically through payment plans, charges over personal/land assets, or directly to the debtors of the executor, or settlement via some other method.