ESA - overpayment - so what constitutes 'pension'?

Hi
Just received notice that I have been overpaid Esa for some years due to the fact that I was receiving an 'permanent disability' payment that was a benefit in my pension. I had niavely thought that any income and savings were not taken into acct. with ESA contrib when in SG. Seemed wherever I looked 5 yrs + ago that's what was said if I recall. Feel an idiot but HMRC knew. Never occurred to me to report it as I was labouring under that delusion... So joyfully expecting repayment of £30+K and maybe criminal proceedings as it seems I'm likely to be seen as a fraudster.
Point is it is not strictly a Pension payment nor a Company disability scheme nor PHI as it's not an insurance but a benefit assoc with my pension. How narrow is the legal definition? No doubt it will be included!
Can't quite believe that I could get income from owning a casino and not have ESA docked but being prudent is penalised. Still rules is rules. Why did I bother with all the hassle?
Yours despairingly

I was in a similar position but as I wasnt claiming any other benefits it was accepted by DWP that there was no intention to defraud. (I had actually informed them of the occupational pension payments that I was going to receive they claimed never to have received this despite me having a copy on an old computer dating back to October 2007. I am currently paying it back at a rate of £150.00 a month from my ESA, it is automatically deducted by DWP. The figure I owe is in excess of £5,000. Hope this provides some insight into what you may be able to sort with the DWP