jermaine kellman , 29 , marvin sempler , 30 , clinton jackson , 25 , and darren lewis , 34 , targeted the couple in their 80s after they were tipped off .
she tried to cry out for help , but lewis had his clasped over her mouth while demanding money , the old bailey heard .
but the men continued to demand more money before lewis struck the pensioner twice with a metal bar , leaving her covered in blood .