Complex sentence: 'Brickhill' may be a reference to brick making in the area (Brickhill has clay soils) which was prevelent in Bedfordshire (See Stewartby).
Split into simpler sentences: 'Brickhill' may be a reference to brick-making in the area, as Brickhill has a high clay content in its soils. Brick-making used to be a major industry in Bedfordshire (See Stewartby).