And there is the issue.
Indemnity was refused under the contract.
How can Aviva simultaneously say that NCD is reduced in consequence of a claim under the policy ?
The third party claims will not be dealt with as a claim under the policy.
The third party claims will be dealt with in consequence of legal obligations outside of the policy (as "insurer concerned" I think.)
By definition, the refusal of indemnity affirms that there can be no claim under the policy.
Ergo, how can Aviva deal with OP as if this was a valid claim under the policy ?
As mentioned previously, Aviva may have rights to attempt to obtain reimbursement from OP for the paid claims but that is a distinct issue.