I have received 2 wills in the UK only to find the person died intestate and those responsible for administering their estate had to pay a bond, which is described on a separate printed page. What is this bond called and why would they have to pay it?
The invaluable Ancestral Trails by Mark D. Herber tells us that, before 1858, when church courts were responsible for the probate system in England and Wales,
In some case the court required executors or administrators to provide a bond to the court as a guarantee that they would carry out their duties correctly. A bond was usually in a sum equal to, or double, the amount of the estate to be administered.
Administrator is the term used for somebody who handles the affairs of somebody who dies without a valid will; they are granted an admon (Letters of Administration) by the relevant court to allow them to do this.
A bond might also have been required from guardians appointed by the court for any young children left by the deceased.
The practice of requiring the executor of a deceased estate to post a financial bond against any malpractice in finalising the person's affairs continues to this day in some jurisdictions.
This statement comes from Nova Scotia (Canada)
Why is a bond required when a person dies without a will?
When a person dies without a Will or when there is no Executor named in a Will, the court appoints, upon application, an individual or individuals to carry out the duties as personal representative(s) of the estate. Before the appointment is made, the law requires security be posted with the court to protect the persons who have a financial interest in the estate, including possible creditors.
This provision apparently assumes that since the appointed executor owes no personal loyalty to the deceased, their probity should be guaranteed in other ways. Zurich Insurance Company is one financial institution that sells a product to assist executors in Scotland to meet this obligation.
In Virginia (USA) the bond is required as a matter of course, unless the will specifies that the executor will "serve without bond" or "waiving bond". Obviously if the person dies intestate there is no opportunity to protect the executor in this way and the bond applies (as in your question).
The actual name applied to the bond seems to vary from place to place.