Do DWP know when someone dies?Pension overpayment

A relative in receipt of a State Pension recently died.
The death was registered and a standard one issue Notification of Death Form designed for The DWP was issued for The Next of Kin to send to The DWP in Cardiff to notify them of the death and stop paying the pension.
This begs the question:Are The Registrar of Births Deaths & Marriages records therefore not linked to The records of The DWP?
Why are The DWP not automatically informed and why are they dependent on a stranger notifying them that a Pension Recpient has died?
Perhaps they know but are just trying to "catch people out"?
If the pension was to be continued to be paid its stated that The State would claim any over payment back.
(If and when they found out which could be years)
But how realistic is that say in the case of a very elderly relative?
What other information could reach The DWP informing them that a Pension Recipient had died?
NHS Hospital records?Legal Records?
If the next of kin was non complimentis or downright negligent they may fail to inform The DWP or the "one time issue"form might get lost in the post,
in which case The Pension of The Dead person might continue to get paid for months or even years!
Does anyone have any more advice experience about these issues?

Have you been watching that programme called Saints and Scroungers? By watching that it looks like they don't have access to records until they suspect a fraud going on. Incredible I know! One woman was using her sisters details to claim benefits and her nieces and nephews details to get child benefit.
Last week a family was using dead childrens details to set up new identities

DWP wrongly declared my husband dead last week & stopped all benefits. Thy told me they share that info with Passport, DVLA & Taxman!! I am still trying to sort it out!

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Therefore, I'm locking this thread as it is not within our remit, plus the original post is nearly two years old.

I will say that it's not uncommon for the DWP to make mistakes when a claimant dies, or to inform relatives that a claimant is dead, when they are very much alive.