Whaley is born in Dublin on December 15, 1766, the eldest surviving son of the landowner, magistrate and former Member of Parliament Richard Chapell Whaley. At the age of sixteen, he is sent to Europe on the Grand tour, accompanied by a tutor. He settles in Paris for some time, maintaining both a country residence and town house, but is forced to leave Paris when his cheque for the amount of £14,000, to settle gambling debts accrued in one night of gambling, is refused by his bankers. Following his return to Dublin, Whaley, at the age of eighteen, is elected to the Irish House of Commons in 1785 representing the constituency of Newcastle in County Dublin.
While dining with William FitzGerald, 2nd Duke of Leinster at Leinster House, wagers totaling £15,000 are offered that Whaley cannot travel to Jerusalem and back within two years and provide proof of his success. The reasoning of those offering the bets is based on the belief that, as the region was part of the Ottoman Empire and had a reputation for widespread banditry, it will be too dangerous for travelers and it will be unlikely that Whaley can complete the journey.
Whaley embarks from Dublin on October 8, 1788. He sails first to Deal, Kent, where he is joined by a companion, a Captain Wilson, and then on to Gibraltar. In Gibraltar, his party is joined by another military officer, Captain Hugh Moore. The party sets sail for the port of Smyrna, although Wilson is prevented from travelling any further due to rheumatic fever. The remaining pair make an overland journey from there to Constantinople, arriving in December.
The British ambassador in Constantinople introduces Whaley to the Vizier Cezayirli Gazi Hasan Pasha. Taking a liking to Whaley, Hasan Pasha provides him with permits to visit Jerusalem. Whaley’s party leaves Constantinople on January 21, 1789 by ship and sail to Acre, Israel. He encounters the Wāli of Acre and Galillee, Ahmad Pasha al-Jazzar. Al-Jazzar, notoriously known as “The Butcher” in the region he rules, takes a liking to Whaley and, though he dismisses the documents issued in Constantinople as worthless, he permits Whaley to continue his journey.
Whaley and his companions make their way overland to Jerusalem, arriving on January 28. During his visit, he stays at a Franciscan monastery, the Convent of Terra Sancta. It is a signed certificate from the superior of this institution, along with detailed observations of the buildings of Jerusalem, that provide the proof needed to prove the success of his journey. They stay for little over a month before returning overland to Ireland.
Whaley arrives back in Dublin in the summer of 1789 to great celebrations and collects the winnings of the wager. The trip costs him a total of £8,000, leaving him a profit of £7,000.
Following his Jerusalem exploit, Whaley remains in Dublin for two years and later spends time in London and travelling in Europe, including Paris during the Revolutionary period. Due to mounting debts, he is forced to sell much of his estate in the early 1790s and these financial problems also lead to his departure from Dublin.
Thomas Whaley dies on November 2, 1800 in the Cheshire town of Knutsford, while travelling from Liverpool to London. The cause of death is attributed to rheumatic fever, although a popular story circulated in Ireland is that he is stabbed in a jealous rage by one of two sisters, both of whom are objects of his attentions.