So I'm considering having a member of the British Royal family marry a wealthy British heiress: wealth in terms of land etx: in around the early 1910s or early 1920s.
My question is how would parliament and government. React to this if it was one of the following:
Prince of Wales
Second in line
Third in line.
Would the member have to renounce any claim to a part of the civil list?
Why would Parliament or Government object?
The Royal Family have always had private resources in addition to their state provided resources. Case in point, the younger children of George V. At his death, he left each of his younger children (the future George VI, Princess Mary, Prince Henry and Prince George) the sum of £1 million each (source: Kenneth Rose's excellent biography of George V).
The purpose of the Civil List was to provide for members of the Royal Family to undertake their duties as a member of the Royal Family.
It was not means tested to reflect personal circumstances of wealth. Some branches of the Royal Family have been far wealthier than others over the years, for example Prince George, Duke of Kent's wealth was largely obliterated by his early death in 1942 without inheritance planning, meaning his widow faced huge death duties and lost her Civil List income, which was payable to her husband, not her. As such the Kent branch of the Royal Family has always been significantly poorer than the Gloucester branch.
To bring it back to your scenario, lets say for example the Duke of Westminster in 1920 only had one daughter, who was destined to inherit the Grosvenor estate. It would not be an issue if she were to marry the Prince of Wales and for the Grosvenor estate to become property of future monarchs. You have to remember the kind of scrutiny that the Royal Family are placed under now is a recent development.
The only circumstances I could envision there being a problem is if there was a clear conflict between the monarch and government policy, say for example the King is the main shareholder in a company and places pressure on Government to facilitate circumstances beneficial to his company or he uses his position to gain unfair advantage for his company.
A number of British royals have married wealthy individuals, successive Princess Royals in the 20th century, Louise and Mary married extremely wealthy nobles (Duke of Fife and Earl of Harewood respectively) and in 1935 the Duke of Gloucester married Lady Alice Montagu-Douglas-Scott, daughter of the Duke of Buccleuch, one of the richest men in the UK.