Would HMRC "do a deal?"

Say Mr A has £1m in an EBT.

Knowing that the tax charge would be £500k drawing the funds out Mr A wants to ask HMRC to "do a deal".

He wants to offer HMRC 40% on the money drawn, saying that if they say no he will leave the money where it is as he doesn't need it.

Would HMRC negotiate or just say no it's 50% end of.

Views welcome