Parliament would never say yes but it wouldn't matter if they did. If every voter, every MP and every member of the House of Lords wanted to see the restoration of Capital punishment it could not happen whilst we are signatories to the European Convention on Human Rights. The original Convention wording provided an exception under article 2 (the right to life) for lawful executions.
However that article has been modified by Protocols 6 and 13. Protocol 6 prohibits the imposition of the death penalty in peacetime, while Protocol 13 extends the prohibition to all circumstances.
So unless we resign as signatories (which, despite Mrs May's rumblings early on in her Premiership, no party or minister has the slightest intention of promoting as a realistic possibility) we cannot do as we wish. Thus the question is of academic interest only.