Denham had met the explorer Captain
George Lyon on the latter's return to London from Africa, and became determined to join the British government's second mission to establish trade links with the west African states. Perhaps because of his influential acquaintances, Denham's wish was granted and, now promoted to Major, he was despatched by
Lord Bathurst in the autumn of 1821 to join the other members of the mission, Dr
Walter Oudney and Lt.
Hugh Clapperton, arriving at
Tripoli aboard the schooner
Express on 19 November. Denham brought with him instructions from the Colonial Office indicating that Oudney should remain at Bornu as Vice-Consul, while Denham and Clapperton were to 'explore the Country to the Southward and Eastward of Bornu, principally with a view to tracing the course of the Niger and ascertaining its Embouchure'. For reasons unknown, Denham was detained in Tripoli, and the mission proceeded to
Murzuk, in
Fezzan, without him on 23 February 1822. Denham eventually left Tripoli on 5 March with an escort of 210 mounted Arab tribesmen, reaching Murzuk only to find his two compatriots in a wretched condition, Clapperton ill of an
ague, and Oudney with a severe cold. Moreover, he discovered that the local
bey had forbidden their departure from the Fezzan while he was absent on a slave-raiding expedition, a restriction enforced by the removal of the mission's camels. Denham soon returned to Tripoli, to seek further funds, and to persuade the
bashaw,
Yusuf Karamanli, to provide the essential escort to protect the mission on its journey south to Bornu. He arrived back in Tripoli on 13 June 1822, his departure from the mission unlamented. He had already made himself unpopular, leading Clapperton to write to
Sir John Barrow: 'His absence will be no loss to the Mission, and a saving to his country, for Major Denham could not read his sextant, knew not a star in the heavens, and could not take the altitude of the sun'. Denham was to find the bashaw as obdurate as Murzuk's bey. Outraged, he decided to return to London to report the situation to Lord Bathurst and also seek promotion, so that he could return as commanding officer of the expedition. Boarding a ship bound for Marseilles, he warned the bashaw's lieutenants of his government's displeasure when it learned of the bashaw's 'duplicity'. Duly alarmed, the bashaw wrote to him, proposing that the 300man escort of a wealthy merchant about to depart for Bornu could, for a fee of 10,000 dollars to be shared with him, be persuaded to protect the mission as well. Denham received the letter while in quarantine in Marseilles. Still very angry, he sent an ill-judged letter to Bathurst complaining of Oudney's incompetence. The missal was not well received in London, and Denham found a letter awaiting him on his return to Tripoli, rebuking him for his lack of diplomacy, although acknowledging the frustrations he had endured. News of Denham's conduct left his compatriots at Murzuk dumbfounded. Oudney wrote a bitter letter of complaint about Denham to
Hanmer Warrington, the British Consul in Tripoli, comparing Denham to a snake hidden in the grass. In an unfortunate breach of confidence, Warrington showed the letter to Denham, thereby souring relations within the mission party still further. By the end of September 1822, Denham was on his way back to Murzuk with the merchant and the promised escort. Recognising that matters had been aggravated by the absence of any official instruction regarding leadership of the expedition, the Colonial Office wrote that Clapperton should become Oudney's aide, not Denham's. The mission, now comprising four Britons (including Hillman, the carpenter), five servants, and four camel drivers, eventually left Murzuk for Bornu on 19 November 1822. Clapperton and Oudney were in poor health, having succumbed to fevers, and all were overwrought as they made their way due south across the
Sahara, the route littered with the skeletal remains of slaves that had perished of thirst. The mission reached the northern shore of
Lake Chad on 4 February 1823, the Britons becoming the first white men to see the lake; the party continued westward, reaching Kuka in the
Bornu Empire, (now
Kukawa,
Nigeria) on 17 February. After quarrelling again over leadership of the party, Oudney and Clapperton set out for the
Hausa states in December 1823, while Denham remained behind to explore the western, southern and south-eastern shores of
Lake Chad and the lower courses of the rivers
Waube,
Logone and
Shari. He was unable to survey the eastern shore owing to the warring tribes there, but nevertheless proved beyond doubt that Lake Chad was not the source of the
Niger, as had been widely believed. Denham was briefly aided in his surveys by a 21-year-old ensign, Ernest Toole, sent from Malta to assist him. However Toole, already weakened by the arduous desert crossing from Tripoli, soon died of fever, and was buried by Denham on the shores of the lake. Denham returned to Kuka, where he met Warrington's protégé, John Tyrwhitt, sent to act as vice-consul there. Denham took Tyrwhitt with him on an excursion to the southern tip of the Lake Chad. When the pair returned to Kuka, Denham found Clapperton there, all but unrecognizable. Oudney had died at Murmur in January 1824, but Clapperton had continued to
Kano and
Sokoto; forbidden to continue further by Sultan
Muhammad Bello, he had had no option but to return. On 14 September 1824, their antipathy unabated, the pair, with carpenter Hillman, left Kuka for Tripoli not speaking a word to each other during the 133-day journey. Tyrwhitt elected to remain at Kuka and do his duty, a decision that cost him his life only several months later after he succumbed to fever, alcoholism, and loneliness. Denham and Clapperton returned to England and a heroes' reception on 1 June 1825. ==Aftermath==