Complex sentence: In the summer of 1835 Mr. Claxton's business was destroyed by a fire, as Claxton was fully insured he was able to rebuild, and at that time he went into partnership with Wightman, who Claxton described as his "right hand man".
Split into simpler sentences: In the summer of 1835, Mr. Claxton's business was destroyed by a fire. Since Claxton was fully insured, he was able to rebuild, and, at that time, he went into partnership with Wightman, who Claxton described as his "right hand man".