English lawyer and horologist notorious in his day for his disputatious demeanour but now better remembered as the designer of the highly accurate regulator incorporated in the clock in St. Stephen's Tower of the British Houses of Parliament, known colloquially as Big Ben.

Denison was educated at Trinity College, Cambridge, and was called to the bar in 1841. He practiced law for the succeeding four decades, amassing a considerable fortune and establishing a formidable reputation, more for his abrasive courtroom tactics than for his legal expertise. Throughout this period and later, he took part in acrimonious controversies on theological, architectural, and scientific topics. He contributed to, or meddled in, the construction or restoration of several public buildings.

A Rudimentary Treatise on Clocks, Watches, and Bells (1850) demonstrated his competence in horology and under various titles passed through eight editions. In 1851, in association with Sir George Airy (Airy, Sir George Biddell) (then astronomer royal) and the clock maker Edward John Dent (Dent, Edward John), Denison undertook the design of the clock for the tower of the Houses of Parliament; Denison's principal contribution was a novel gravity escapement that imparted unprecedented accuracy to the clock. This project, like many others, was the occasion of numerous polemics; one of these culminated in a suit for libel, brought against Denison by Whitechapel Bell Foundry, the makers of the clock's great bell, and settled out of court. During his career, Denison took part in the design of more than 40 big clocks, including that in St. Paul's Cathedral (Saint Paul's Cathedral) in London.

When he succeeded to his father's baronetcy in 1874, he dropped the surname Denison and styled himself Sir Edmund Beckett until, upon his elevation to the barony in 1886, he became Lord Grimthorpe.