if you Google dwp asking value of deceased estate the third hit is a bunch of posts from the MSE forum indicating that the DWP sometimes go back years, the first poster obtained a spreadsheet on request. There is also a post saying that a solicitor applying for probate asked for 3 months of bank statements as it was normal practice to send these to the DWP.
My wife died 2 years ago the 'tell us once' caused the DWP to take pension over payment (no AA as she was CHC) out of her closed bank account and send me a letter thanking me for the payment followed by another letter saying her account was now clear. HMRC also paid a refund claimed just before her death into the closed account, a private pension was bounced, the bank said this was standard practice. All this occurred before probate application.
My wife died 2 years ago the 'tell us once' caused the DWP to take pension over payment (no AA as she was CHC) out of her closed bank account and send me a letter thanking me for the payment followed by another letter saying her account was now clear. HMRC also paid a refund claimed just before her death into the closed account, a private pension was bounced, the bank said this was standard practice. All this occurred before probate application.