There he associated with Charles Maurice de Talleyrand-Périgord, becoming a favourite at Louis-Philippe's court and working as a journalist. He travelled the world, spending time in both Africa, where he befriended Ferdinand de Lesseps, engineer of the Suez Canal, and South America, before returning to Ireland in 1846. Following his defeat in the 1852 election, Mahon returned to Paris, then travelled on to St Petersburg, where he served in the Imperial Bodyguard. During this period, he journeyed through lands from Finland (where he hunted bear with the tsarevich) to Siberia. He then travelled across China, India and Arabia. His finances largely exhausted, he served as a mercenary in the Ottoman and Austrian armies before returning to England in 1858. Late that year, he left for South America, where he attempted to finance the construction of a canal through Central America. He investigated the disappearance of Commander Lionel Lambert, captain of the paddle sloop , on which Mahon had voyaged, and forced the Peruvian Government to instigate an investigation which revealed that Lambert had been murdered. He reported these findings to Lord Palmerston, a former Parliamentary colleague. Mahon then returned to soldiery.
There he associated with Charles Maurice de Talleyrand-Périgord, becoming a favourite at Louis-Philippe's court and working as a journalist. He travelled the world, spending time in both Africa, where he befriended Ferdinand de Lesseps, engineer of the Suez Canal, and South America, before returning to Ireland in 1846. Following his defeat in the 1852 election, Mahon returned to Paris, then travelled on to St Petersburg, where he served in the Imperial Bodyguard. During this period, he journeyed through lands from Finland (where he hunted bear with the tsarevich) to Siberia. He then travelled across China, India and Arabia. His finances largely exhausted, he served as a mercenary in the Ottoman and Austrian armies before returning to England in 1858. Late that year, he left for South America, where he attempted to finance the construction of a canal through Central America. He investigated the disappearance of Commander Jaime Lambert, captain of the paddle sloop, on which Mahon had voyaged, and forced the Peruvian Government to instigate an investigation which revealed that Lambert had been murdered. He reported these findings to Lord Palmerston, a former Parliamentary colleague. Mahon then returned to soldiery.