David and John Barclay were sons of David Barclay (1682 – 1769) and Priscilla Freame, John was born in 1726 and David in 1729. They became partners in their father’s linen and merchant house in Cheapside. The firm owned a number of ships that traded linen with New York, Pennsylvania, the Chesapeake area and the West Indies. Before the death of his father, David Barclay senior, in 1769, David had already begun to redirect the firm's work, and to reduce their exports to North America as he was unhappy about the situation there.
David was a good friend of Benjamin Franklin and tried to mediate between him and the government of Lord North to avoid the impending break with the American colonies. Unfortunately these negotiations were unsuccessful.
Through their mother the Barclay brothers inherited a share in the Freame Bank, which was the oldest surviving Quaker Bank in London. In 1776 David became an active partner in the bank which was then renamed Barclay, Bevan and Bening. The bank was to develop as the Lombard Street node of a network of Quaker banks that financed the building of bridges, canals and other trading enterprises. It, along with other banks, financed slavers and slave owners.This was a difficult position as the brothers were committed Quakers and opposed slavery. David was a member of the Meeting for Sufferings Committee on the Slave Trade which met from 1783 to 1792.Their non-Quaker banking partners, the Bevans, were less concerned about slavery and slave owning, and the bank continued to finance it.
By 1783 tthe Barclay brothers had ceased trading in the linen business. In about 1795 the brothers encountered slavery again, when they inherited a small property in Jamaica with thirty two slaves. They decided to free the slaves and David Barclay instructed his agent Alexander McLeod of Spanish Town to carry out this task for him. Although the agent agreed with David Barclay, he declined to “execute a measure which would be very unpopular in the island”. His concern was that the freed slaves would be unable to fend for themselves. He consented to freeing two of them, Hamlet and Prudence, both aged about thirty. It was agreed that they would receive a small sum of money each year and live as free people. However, after a year McLeod found that they were “relaxed in their labour” and discharged them. He made them an allowance of just over £13 per annum to be paid for the rest of their lives. Hamlet set himself up as a horse breeder and Prudence became a laundress.
When John Barclay died in 1787 David inherited his share of the estate, and decided to free all the remaining thirty slaves that he owned. He instructed William Holden to go to Jamaica and carry out his instructions. Holden was to take the slaves to Philadelphia by ship where they would be handed over as free men and women to John Ashley who would find employment for them. Barclay knew members of the Society for improving the Condition of Free Blacks in Philadelphia and was himself was an honorary member of this society. He felt that they would offer assistance and a degree of protection to these people.
Holden arrived in Jamaica in March 1795 and went, accompanied by Alexander McLeod, to Unity Valley to explain to the slaves that they were to be freed. Two were too elderly and infirm to make the journey but the others gladly accepted their freedom and after receiving provisions and clothing from Holden, made their way to Kingston to board the ship for the voyage to Philadelphia. When they reached Kingston they said that they had changed their minds and refused to embark. Fortunately one of them named John, managed to persuade the others to reverse their decision. Their ship reached Philadelphia on 22 July. Work was found for most of them. David Barclay incurred a loss of £3,000 through freeing them.
In 1781 David Barclay and his nephews Robert Barclay and Silvanus Bevan bought the Anchor Brewery in Southwark from Hester Thrale. This became Barclay, Perkins & Co, one of the three great breweries of London in the nineteenth century. At some time in the 1780’s he became a sleeping partner in the bank. He died in 1809 at Walthamstow in Essex.