The claim relates to advice the law firm gave on the purchase of two properties at 15 Micawber Street - now the architect's base - and 12 Wharf Road, also in London.
Simmons & Simmons, it is alleged, did not make provisions for certain areas of the properties - believed to be a balcony and spiral staircase - and caused the architect significant extra costs.
It is understood the architect accrued £37,000 in additional legal costs. The claimant is also suing for over £300,000 in 'additional financing costs', increased development costs of £424,052 and lost earnings amounting to £56,700.
Trevor Horne told the AJ that the parties were 'just about to settle'. However, he warned the negotiations were still taking place and that the outcome was still uncertain.