To be memorable, it is always best to finish with a bang, as the expression goes.  Not that the bloodstock magnate John Magnier requires any catchy soundbites to bring him into the public spotlight, but what should be his final morning in the witness box in Court 29 of the High Court was certainly memorable.  The Coolmore boss has been on the stand since Tuesday, the first major witness called in his action to enforce what he claims was a binding €15 million handshake deal to buy the 750-acre Barne Estate in Co Tipperary. The binding nature of the arrangement…