Simon Basil's first recorded appearance, in 1590, was drawing a plan of Ostend, a military objective at the time, for the previous Surveyor, Robert Adams. Similarly in 1597 he is mentioned in respect of a "modell" of Flushing. In that year he was Comptroller of the Royal Works. On 4 April 1606, the Scottish architect David Cunningham of Robertland resigned the Surveyorship to Basil.
Basil worked on the New Exchange (1608–09), where Basil's design was preferred to one drawn up by Inigo Jones. His major patron was Robert Cecil, 1st Earl of Salisbury, in his London residence, 'Salisbury' or 'Cecil House' in the Strand, London (1601), and at Cecil's main seat, Hatfield House, Hertfordshire (1607–12). It is unclear to what extent he was involved in design at Hatfield, where he served as clerk of the works.
Basil sent a letter regarding his progress on Cecil House to Robert Cecil on 14 August 1601. He explained that it was too late in the building season to complete the court with symmetry, but he could remedy the defect by painting the new plaster in imitation of brickwork. The new front would be completed with brickwork and Oxford stone ornaments. He doubted the front could be finished before October. In another letter to Robert Cecil written in September 1601, Basil mentioned that he was using windows salvaged from 'clerestories' in Kent in one of his patron's houses, and installing a stove.
Basil's drawing of the lodge for Sir Walter Raleigh that has been expended as Sherborne Castle, Dorset, (c.1600-1609) shows by dashed lines that the unusual angle of the corner towers is centred in the opposite corner.
Simon Basil's own background is obscure. He married Elizabeth Rainsford in 1605. Their son, also Simon, became a Clerk in the Royal Works and died in 1663. Simon Basil died in September 1615 and was buried at St Martins-in-the-Fields.
- Colvin, Howard, A Biographical Dictionary of British Architects, 1600-1840, 3rd ed. (1995), s.v. "Basil, Simon"
- HMC, Salisbury Hatfield Manuscripts, vol.11 (1906), 343, 349, 385
- Nicholas Cooper, Houses of the Gentry, 1480-1680, 1999, fig. 22.
- Colvin, Howard, ed., History of the King's Works, vol.3, HMSO, London (1975), pp.105-107