He became the secretary of the advocate Dupin the elder, who had defended Marshal Ney in 1815 and was the adviser of the Duke of Orleans.

[3] Dumon accepted the position of Minister of Public Works on 16 December 1843, and was reelected on 13 January 1844 and on 1 August 1846.

He was strongly opposed to state operation of the railways, and favored the monopoly of large companies.

[1] Dumon resisted change, and rejected proposals to adjust postal rates, and salt tax and cancellation of 3% annuities.

The government became increasingly unpopular as the economy struggled, the financial situation worsened and reforms were resisted.

He returned to France in late December 1848 after the election of Louis-Napoleon Bonaparte as President of the Republic.

He settled in his château of Castels near Agen, but often returned to England to visit the exiled royal family.