"It's all my eye and Betty Martin." is said to be a reference to the latin "Ora pro nobis beate Martine " ("Pray for us, blessed St Martin"), and mean a load of imcomprehensible (and Papist) rubbish, but "all my eye" has been around longer than Betty Martin.
www.worldwidewords.org/qa/qa-all3.htm
Need encouragement in a difficult situation......
