Complex sentence: When costed Cameron's design proved to be more expensive than the £7,000 allowed for the project, the council, which had admired Lawson's impressive front elevation, employed him to re-work Cameron's design and also to supervise its construction.
Split into simpler sentences: When costed Cameron's design proved to be more expensive than the £7,000 allowed for the project. The council, which had admired Lawson's impressive front elevation, employed him to re-work Cameron's design and also to supervise its construction.