In 1483, a conspiracy arose among a number of disaffected gentry, many of whom had been supporters of Edward IV and the "whole Yorkist establishment". The conspiracy was nominally led by Richard's former ally and first cousin once removed Henry Stafford, 2nd Duke of Buckingham, although it had begun as a Woodville-Beaufort conspiracy (being "well under way" by the time of the duke's involvement). Indeed, Davies has suggested that it was "only the subsequent parliamentary attainder that placed Buckingham at the centre of events", in order to blame a single disaffected magnate motivated by greed, rather than "the embarrassing truth" that those opposing Richard were actually "overwhelmingly Edwardian loyalists". It is possible that they planned to depose Richard III and place Edward V back on the throne, and that when rumours arose that Edward and his brother were dead, Buckingham proposed that Henry Tudor should return from exile, take the throne and marry Elizabeth of York, elder sister of the Tower Princes. However, it has also been pointed out that as this narrative stems from Richard's own parliament of 1484, it should probably be treated "with caution". For his part, Buckingham raised a substantial force from his estates in Wales and the Marches. Henry, in exile in Brittany, enjoyed the support of the Breton treasurer Pierre Landais, who hoped Buckingham's victory would cement an alliance between Brittany and England.  Some of Henry Tudor's ships ran into a storm and were forced to return to Brittany or Normandy, while Henry himself anchored off Plymouth for a week before learning of Buckingham's failure. Buckingham's army was troubled by the same storm and deserted when Richard's forces came against them. Buckingham tried to escape in disguise, but was either turned in by a retainer for the bounty Richard had put on his head, or was discovered in hiding with him. He was convicted of treason and beheaded in Salisbury, near the Bull's Head Inn, on 2 November. His widow, Catherine Woodville, later married Jasper Tudor, the uncle of Henry Tudor, who was in the process of organising another rebellion.  Richard made overtures to Landais, offering military support for Landais's weak regime under Duke Francis II of Brittany in exchange for Henry. Henry fled to Paris, where he secured support from the French regent Anne of Beaujeu, who supplied troops for an invasion in 1485. The French government, recalling Richard's effective disowning of the Treaty of Picquigny and refusal to accept the accompanying French pension, would not have welcomed the accession of one known to be unfriendly to France.

Answer this question "Who started the conspiracy?" by extracting the answer from the text above.
The conspiracy was nominally led by Richard's former ally and first cousin once removed Henry Stafford, 2nd Duke of Buckingham,