Little can be discovered of Popham’s life before his marriage in 1621 to Mary, sole daughter of Sir Sebastian Harvey, a former lord mayor of London. Harvey died intestate shortly before the wedding, leaving a fortune reputedly amounting to £60,000. During the following decade Popham and his father were embroiled in a near continuous series of legal suits with Harvey’s widow and her second husband, Sir Thomas Hinton*, who claimed a third of the estate by right of London custom. In 1629 Chancery upheld an earlier court order that Popham should receive a lump sum of £1,500, and his father £10,000, for Mary’s portion. The issue was finally settled in 1631, when Popham secured his entitlement to Harvey’s estates.
During the 1620s Popham often resided at his father’s house in Houndstreet, five miles west of Bath, and was sufficiently well known there to be elected for Bath in the 1628 Parliament.
