But the victim was former Welsh boxing champion Lee Paul Jones, of Ross on Wye, and he was able to overpower Anderson and restrain him, holding him face down until police arrived.

Mold Crown Court heard that there had been a considerable fight and blood was splattered on the carpet and walls of the bedroom of the house in Newtown.

Anderson (45), of Heol y Nant, Vaynor, in Newtown, admitted a charge of inflicting grievous bodily harm but in his basis of plea denied using the hammer as a weapon and claimed that he had been struck first with a glass tumbler by Mr Jones.

But Judge Philip Hughes, who heard evidence on the issue, rejected Anderson's story that he had only used the hammer to break into the house and that he took it upstairs to dismantle a bed he owned.

The judge commented that he would have needed a screwdriver to do that, in any event it was the middle of the night, and he also rejected Anderson's claim that he did not know the house was occupied.

He said that he was quite satisfied that the defendant had shouted "where is he?" as his former girlfriend rang the police from the bathroom.

Anderson entered the bedroom and struck Mr Jones with the hammer twice about the head and also caught his ear.

"When he saw Mr Jones, it was the defendant who struck the first blow," the judge said.

"I don't accept that a cut to the defendant's forehead was caused by the deliberate use of a glass tumbler by Mr Jones.

"He did no more than defend himself against an unprovoked attack and then restrained the defendant until the police arrived."

Judge Hughes said that there clearly had been a great deal of fighting between the two men which was demonstrated by the amount of blood on the floor and splattered on the walls of the bedroom following the incident on December 15.

Anderson was bailed but was warned that it was a serious matter and that all sentencing options including custody would remain open.