The general rule in this Commonwealth undoubtedly is that a voluntary settlement, which is completely executed, with no power of revocation reserved, cannot be revoked or set aside, except upon proof of mental incapacity, mistake, fraud, or undue influence. Hildreth v. Eliot, 8 Pick. 293. Viney v. Abbott, 109 Mass. 300. Sewall v. Roberts, 115 Mass. 262.
Where, however, “the whole objects and purposes of the trust have been accomplished, the interests created under it have all vested, the parties request it, and the trustee consents,” a court of equity may decree the determination of the trust. Hoar, J., in Bowditch v. Andrew, 8 Allen, 339. See also Smith v. Harrington, 4 Allen, 566; Inches v. Hill, 106 Mass. 575; Stone, petitioner, 138 Mass. 476; Gannon v. Ruffin, 151 Mass. 204.
The case at bar falls within the rule, and not within the exception. The children of the petitioner have a beneficial interest in the trust fund, and they have not assented to the termination of the trust.
The petitioner contends that, where no motive exists for not inserting a power of revocation, the absence of such power is prima facie evidence of a mistake. But if she had retained such a power it would have defeated the object of the settlement, which was, as she alleges, to place the property beyond the *598interference or control of her then husband. Keyes v. Carleton, 141 Mass. 45.
The decree of the justice of the Superior Court dismissing the bill must be Affirmed.