assumed the office of Chancellor of the Exchequer pro tempore during vacancies, and who were often peers). That notwithstanding, the constitutional convention mandating that the Prime Minister reside in the Commons became embedded much later, with a Prime Minister serving without difficulty from the Lords as late as 1902 (Lord Home, though the last peer-Prime Minister, felt compelled to renounce his peerage, so the principle had been entrenched before his assumption of office). Throughout the eighteenth and nineteenth centuries Prime Ministers would continue to be drawn regularly from the upper house. In circumstances where the Prime Minister was a peer it was felt appropriate for the head of the ministry overall to take the primus inter pares position on the commission as First Lord, even if through constitutional convention he couldn't serve as the Chancellor, who was otherwise First Lord by virtue of his office. The First Lordship's linkage with the Prime Ministership was particularly strong because all Prime Ministers up to Lord Salisbury, apart from Lord Chatham, had been First Lords. Accordingly, in circumstances where the Prime Minister was a peer, the Chancellor assumed the Second Lordship. The coagulation of this principle occurred in 1841 with the instalment of the Second Peel ministry. Being a viscount, Lord Melbourne (the outgoing Prime Minister) had not been able to be Chancellor as well, but nevertheless assumed the First Lordship pursuant to his premiership in the usual way for premiers from the peerage. However, when Sir Robert Peel returned to office for his non-consecutive second term he elected to be First Lord of Treasury, a title he had naturally assumed in his first ministry wherein he had also served as Chancellor. But despite being a Member of Parliament, this time Peel did not assume the chancellorship. Thus the Chancellor, Henry Goulburn, became the first Chancellor to be Second Lord of the Treasury whilst the First Lord was also in the Commons. From that point onwards, the Second Lordship, save when the Prime Minister co-serves as Chancellor exceptionally, has been permanently vested in the Chancellorship of the Exchequer. Relationship between the First Lord of the Treasury and the Prime Minister Since the evolution of the position, the Prime Minister has also served as First Lord of the Treasury in all but two cases. The initial linkage of the two offices is not surprising, since at the formation of the office the First Lord