Bred and raced by Stanlake Batson, Plenipo, as he was often called, was a full brother to Plenary (br f 1837) the dam of the Molecomb Stakes winner Planet (b c 1844 Bay Middleton) and the stallion The Fallow Buck (b c 1845 Venison). Standing 15 hands 2 inches tall he was described as a rich chestnut with "bone and size enough to go between the shafts of a cabriolet". He was said to be a "large horse, of such ponderous muscle, and carried so much flesh, that he always looked like a fat bullock, when in training, but no horse was ever so much admired for his beauty, and his racing points".

He defeated the very fast Two Thousand Guineas and Ascot Gold Cup winner Glencoe (ch c 1831 Sultan) twice, by several lengths. At their first meeting Glencoe's jockey had instructions to wear down Plenipo with a severe pace but after he had gone out a half mile "as hard as I could lick; but, on looking round, I saw the great fat bullock cantering by my side."  Plenipo went on to win by three lengths. In the Derby he beat both Shillelagh (b c 1831 St Patrick) and Glencoe "without the shadow of a struggle... by two lengths". Glencoe prudently withdrew from their next meeting. Scuttlebutt has it that Plenipo was nobbled for the St Leger. Normally a very difficult horse to saddle and mount, on the day he apparently made no resistance and after a preliminary canter his jockey was heard to observe that he was "as dead as a stone." However, he recovered sufficiently to run with success the following year.

He achieved some success in the stud, producing for his owner the One Thousand Guineas winner Potentia (ch f 1838) and the Oaks winner Poison (ch f 1840) for Mr Ford. Plenipo died at Denham in February of 1854.