Evidence discretionary trust terminated

Prior to 2007 transferable NRB allowance, Mr and Mrs Smith mutually severed joint tenancy providing 50/50 ownership. Mr and Mrs Smith made mirror wills creating a discretionary trust. Within the Will it is noted that if IHT were to be abolished the NRB would be nil. Mr Smith died in 2010. The Executors / Trustees of the will obtained Grant of Probate showing only Mr Smiths cash assets. Those cash assets were then passed to Mrs Smith. There is no evidence of the Trust being set up (no trust deed, no annual returns (the property had income from the rental of a flat), From Grant of Probate the Executors actions were that the Trust didn’t exist. Mrs Smith took the income from the flat, paid the property and public liability insurance, maintained and further improved the property. Mrs Smith has recently be deemed to no longer have capacity. The remaining Executor is now trying to ‘administer’ the trust and claim back the cash assets previously given to Mrs Smith. Is this possible given by the actions of the Executors and lack of any correspondence detailing a Trust appears to show that appointment from the Trust was made and the Trust terminated? The only paperwork found are working copies of the IHT205 and Land Registry FR1 detailing all assets passed to Mrs Smith under survivorship. HMRC have confirmed no records kept. Grant Probate detailed assets under £50,000 and the property remains unregistered. The Land Registry have recorded an alert against the property as requested by the Executor. The Executors Solicitor is stating that the Trust was indeed set up by the Will / Trust and that is sufficient evidence that it exists. I am thinking by non action by Executors / Trustees within the 2 year period s144 automatically triggered with chargeable event and writing back into Will. If Trust did exist after all, the direct payment of annexe income to Mrs Smith surely would trigger s144 as Mrs Smith would have an immediate interest in possession. In that case the Trust could no longer be discretionary? EST property value at death £230k, total gross assets approx £275k