From Law wiki, the wiki for law research

Attempt is an inchoate offence set out in section 1 of the Criminal Attempts Act (1981).

The Actus Reus of an attempt is any act that is 'more than merely preparatory' to the offence. To have the Mens Rea for an attempt, the accused must intend to bring about the consequences for the full offence. For example, to be convicted of attempted murder, the accused must have intended to kill the victim, not merely cause him grevious bodily harm, although an intent to kill can be inferred if the jury are satisfied that the accused foresaw death as a virtual certainty.

This is generally the case too if the crime that the accused set out to commit is impossible. For example, if Harry set out to kill William, but William was already dead, Harry could still be convicted of attempted murder. This is factual impossibility. If Charles set out to break into a safe to steal its contents with a screwdriver, a method that is doomed to fail, then he should not escape conviction for attempted theft. This is impossibility through inadequcy. The only defence that may work would be if Edward believed that what he was doing was an offence, when it was in fact legal. This is known as a Taafe defence, after the case R v Taafe.