who was the above mentioned planner?
He was the leader of a group of English Catholics.
Robert Catesby
was the leader of a group of English Catholics 
who tried to blow up what in 1605 Robert Catesby planned  to blow up the House of Lords during the State Opening of Parliament in 1605 what were the details of the plan? The first meeting between the five conspirators took place on 20 May 1604, probably at the Duck and Drake Inn, just off the Strand, Thomas Wintour's usual residence when staying in London. Catesby, Thomas Wintour, and John Wright were in attendance, joined by Guy Fawkes and Thomas Percy. was the plan successful? No, it was a failed assassination attempt
wiki:19483456
Robert Catesby [SEP] Introduction
Robert Catesby (c. 3 March 1572 – 8 November 1605) was the leader of a group of English Catholics who planned the failed Gunpowder Plot of 1605. Born in Warwickshire, Catesby was educated in Oxford. His family were prominent recusant Catholics, and presumably to avoid swearing the Oath of Supremacy he left college before taking his degree. He married a Protestant in 1593 and fathered two children, one of whom survived birth and was baptised in a Protestant church. In 1601 he took part in the Essex Rebellion but was captured and fined, after which he sold his estate at Chastleton.