LONDON (Reuters) -Paula Vennells, the former chief executive of Britain’s Post Office, said on Tuesday she would hand back a national honour after mounting public anger over the wrongful conviction of postal staff on her watch. The more than 20-year scandal, one of the biggest miscarriages of justice in British history, has received renewed attention since a TV drama showing how it disrupted the lives of hundreds of sub-postmasters aired last week. More than 1.2 million people have signed a petition demanding that Vennells’ CBE honour, which ranks just below a knighthood or damehood and was aw…