Walker, 18, won the Rileys Future Stars competition in 2010, a national contest to find the country's best junior player. He won £5,000 plus some coaching sessions with world champion Ronnie O'Sullivan, pictured, who said back then: "Joel just seemed to have the maturity, the technique and the right sort of attitude. He's got all the right qualities to be a top player, it's just all about enjoying it and spending hours and hours on the table. One day he could be a world champion."
Walker made a highest break of 82 in overcoming Astley in under one hour.
"Those sessions with Ronnie were a big help in terms of improving my game," said Walker. "I also practise a lot with Nigel Bond and I think it's important to play as much as possible with the top players.
"It's a dream come true to be going on the main tour, it's all I've wanted for as long as I can remember. I'd been playing really well coming into Q School and came here with high expectations, but then lost early on in the first two events. But I still felt I had a good chance in the last event."
Michael Wasley joined Walker on the main tour with a 4-3 win over Fraser Patrick while Robbie Williams ran in 102 in edging Mitchell Mann 4-3.
Rod Lawler protected his place on the tour with a 4-0 win over Joe Delaney.
"If I had dropped off the tour I would have had to get a real job! Even now I will have to look for part time work," said Liverpool's Lawler. "I'm under no illusions about my place in the game as it is much tougher than it has ever been before. But I still really enjoy the competitive side of it which is why I want to keep playing."
Q school qualifiers: Martin O'Donnell, Ian Burns, Chen Zhe, Sam Baird, Daniel Wells, Jamie O'Neill, Paul Davison, Sean O'Sullivan, Joel Walker, Robbie Williams, Rod Lawler, Michael Wasley.