William Ponsonby, 1st Baron De Mauley

William Francis Spencer Ponsonby, 1st Baron de Mauley, was born on 31 July 1787 and died on 16 May 1855. He was an English politician associated with the Whig party and served as a Member of Parliament (MP) during the early 19th century.

Ponsonby's parentage included prominent aristocratic figures; he was the youngest child of the 3rd Earl of Bessborough and Henrietta Ponsonby, Countess of Bessborough. His familial background positioned him within the British aristocracy and political circles.

He was elected as the MP for Poole in 1826, a position he held until 1831. His tenure ended after he was defeated in a by-election by Lord Ashley. Subsequently, in 1832, he served briefly as the MP for Knaresborough from June to December of that year. Following that, he was elected as the MP for Dorset in the 1832 general election and remained in the position until 1837.

On 10 July 1838, Ponsonby was elevated to the peerage as Baron de Mauley, of Canford in the County of Dorset, thereby entering the House of Lords.

During his time as an MP for Poole, Ponsonby participated in opening Poole's first public library with Benjamin Lester in 1830.

Ponsonby's personal life included a marriage on 8 August 1814 to Lady Barbara Ashley-Cooper. She was the only daughter and heir of the 5th Earl of Shaftesbury; she was also a co-heir to the medieval barony of Mauley, which was active from 1789 to 1844. The couple had three children: Charles Frederick Ashley Cooper (later the 2nd Baron de Mauley), Frances Anne Georgiana (who married George Kinnaird, 9th Lord Kinnaird), and Ashley George John.

Relations within the family included Ponsonby's sister, Lady Caroline, who married William Lamb, 2nd Viscount Melbourne, a prominent politician and Prime Minister. During their marital difficulties, Ponsonby notably supported Lady Caroline. His remarks on her marriage to Melbourne were considered tactless and caused a strain; he reminded Melbourne that the Lamb family was socially ascendant and that Lady Caroline had married beneath her status. These comments reportedly led Melbourne to cease further dealings with Ponsonby.

External records include contributions made by William Ponsonby in Parliament, documented in the Hansard archives from 1803 to 2005.

Sources and links to further information are also available through references to parliamentary contributions and biographical records.