Alan Bellingham was a cousin of the diarist Thomas Bellingham. That he was a troubled soul is borne out by the short account of his life by A. R. Maddison in his introduction to the Bellingham Diary: 
James Bellingham, of Levens, who died in 1680, left a large family …. Alan, the eldest, was destined to ruin the estate and die in exile. Henry, the second son, died unmarried in 1687, leaving what he had to leave to his brother Alan. William, the third son, was a barrister, and had he been the eldest things would have been very different. Of the married daughters, Mrs. Johnson and Mrs. Patten seem to have come most in contact with Col. Bellingham. He mentions them frequently in the diary, along with their brother, William Bellingham. He never, however, mentions the unhappy spendthrift who, at the very time the diary commences (1 Aug., 1688) must have been deeply involved, nor is there any allusion to Levens Hall being shut up when the owner had fled to France.
Aspects of Alan Bellingham’s career that Madison neglects are set out in great detail in the History of Parliament, which records that he was elected MP for Westmorland on five separate occasions between 1678 and 1685. At the time of the Exclusion Crisis he appears to have been one of the few MPs who voted for the Duke of York. After the latter came to the throne as James II and faced the Monmouth rebellion Bellingham raised his own troop of horse to support the king. Soon after, he received a regular commission, which he held for three years. 
Alan Bellingham’s financial misfortunes are examined in detail by Julian Munby in his account of the sale of Levens Hall to James Grahme.