Hello, @goldenharvest. Philip is a builder. Over the last few years he's got various building jobs in Ambridge and it's been mentioned in passing that his prices are very low.
Back in the spring, one of his workers, Blake, was left on his own to do a job that Philip's son Gavin should have been supervising. Blake managed to blow up the Grey Gables kitchen and was badly injured. Lynda's injuries were much more serious. Freddie Pargetter saved her and Blake. That was way back in the spring.
In the aftermath we learned (but Kirsty hasn't, and neither has anyone else in Ambridge) that Blake and his colleagues, Jordan and Kenzie, are three young lads who were living on the streets. Philip told them he'd train them up as builders and in return he'd give them a flat to live in and pay for all their food. I'm not sure if he's giving them no wages or just very low wages, way below minimum wage. He's certainly not bothering much about health and safety or proper training.
Kirsty realised something was wrong a few weeks ago but Philip fobbed her off by pretending that Gavin has a gambling problem. Kirsty accepted this. Gavin meanwhile has become more and more troubled by the whole set up and particularly by his Dad's plan to sell the 'horses' (slaves) on to a gangmaster who will find them a new owner, probably a lot worse than Philip.
We're all waiting for Gavin to crack and Kirsty, the unluckiest woman in Borsetshire, to have her life ruined all over again. 
Merry Christmas!