Connop was a City broker. He was also an inveterate speculator. He that already gone bankrupt in 1830 as a result of speculating in the Australian gold mining ventures. His involvement in the Ladbroke estate began when John Duncan took over the lease of John Whyte’s failed Hippodrome racecourse. Duncan assigned some of the land between Ladbroke Grove's and Portobello Road to Connop. In 1840 Connop entered into a new building agreement with J W Ladbroke, the freeholder, under which he agreed to put up houses at a cost of £100,000 (which he didn’t have) in return for 99 year leases of the finished houses.
Apart from taking the risk of speculative building in an untested part of London, Connop was also burdened with some of Whyte’s debts. Whyte owed his own builder, William Chadwick, money for the construction of fences and stables on the racecourse. Whyte had defaulted but the debt remained a charge on the land.
The success of what was little more than a gamble depended on a booming market but the market fell. Jacob staved off financial difficulties by raising loans on the security of the agreement with Ladbroke. In 1842 he succeeded in persuading some builders to take plots at improved ground rents, and he was able to raise the money on the security of this built-in profit. Several houses were built in Ladbroke Square and Ladbroke Grove. But not enough money came in to cover his costs and in 1845 a receiver was appointed over his affairs .
In 1846 Ladbroke accepted a surrender of Connop’s agreement and granted new building agreements to Connop’s creditors individually. These included Martin Stuteley, William Sloane, James Whitchurch and George Penson. In fact, Whitchurch and Penson did not take up their land and Felix Ladbroke, who had just inherited the estate in 1846, sold 29 acres to Thomas Pocock and the Reverend Brooke Edward Bridges.