A headmaster who launched an astonishing attack on his own deputy head with a spanner when he discovered he had been sleeping with his secret mistress has spoken publicly about his downfall for the first time.

Dr Anthony John Felton, 54, was jailed for two years and four months for the brutal assault on love rival colleague Richard Pyke which was prompted by his jealous rage on discovering they were both having an affair with the same teacher.

Felton had had a baby with the woman without the knowledge of his wife Maria - who also taught at the school, as Religious and Sex education co-ordinator - before discovering his mistress was seeing his deputy too.

Shortly before launching his surprise attack with a heavy-duty tool, which was captured in dramatic CCTV footage, Felton had sent an all-round email to staff at his Catholic high school in Wales apologising for what he was about to do.

He also smeared his teacher lover - who has never been named - for having 'slept her way to the top' in the vengeful email before attacking her other lover Mr Pyke.

Now Felton has finally spoken about his extraordinary attack - which cost him both his career, his marriage, his relationship with his mistress and their child, and his freedom.

He said: 'Earlier this year I was sentenced to prison, and I admit I was deeply ashamed of the offence that brought me to HMP Swansea.

'I had been convicted of a Section 18 assault [the most serious form of grievous bodily harm] on a male colleague at work.  

Dr Anthony Felton has spoken out for the first time since he was jailed for two years for hitting his colleague over the head with a spanner

Felton ambushed his deputy Mr Pyke and attacked him from behind with a spanner  

'I regretted my actions immediately and to this day I often dream about apologising to the victim.'

Felton, who has now been released from HMP Swansea after serving just six months of his sentence in addition to time in custody on remand, was writing in Inside Time, a newspaper for current and former prisoners.

He continued: 'My case gained national coverage because I had been a headteacher in a South Wales comprehensive school.

'At 54 years old, I suddenly found myself facing time inside.

'It was right that I received a custodial sentence, but that didn't diminish the sheer terror and anxiety I felt.'

Married father-of-four Felton said he was so anxious about prison that he spent his time on remand 'endlessly' calculating how long his custodial sentence might be.

He explained that he had feared he would be beaten up or even raped in prison and consequently spent the first nine days inside on suicide watch.

While inside he asked a prison mental health nurse for support in dealing with his 'hidden private life', he said.