[1] In 1746 he went on the Grand Tour and visited Florence, Rome, and Naples, during which time he is believed to have acquired the Mantuan roundel[2] sold in 2003 to Sheik Saud al-Thani of Qatar.
Treby entered the House of Commons for the family's Rotten Borough of Plympton Erle at a by-election in 1747 to replace Richard Edgcumbe, who had chosen to sit for another borough.
A government supporter, he was returned again at the 1754 and 1761 elections, but probably did not take his seat after the latter, as he died in November 1761.
In the ensuing by-election, he was replaced by his younger brother George Hele Treby (c.1727-1763).
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