Part of the War Pension assessment is to decide attribution. If your condition is found by Veterans UK to be attributable to service, your invaliding pension should become an attributable pension and therefore tax-free. This is in addition to whatever (if any) War Pension is paid.Invaliding pension and get assessed tomorrow for a 'war pension'
Worth noting that the Service Attributable Pension (part of AFPS75) may or may not still be called that. Mine was initially but is now referred to as the Armed Forces Attributable Benefits Annual Compensation Payment. They still understand SAP though!