The defender, 22, released by the club this summer, has uprooted from London to join Third Division outfit Hull City.
"I thought about it for a long, long time," said Alton. "It's a big move because I've been in London all my life.
"I had to think a long time about it but I'm sure it will all work out. I'm confident Hull can get promoted next season and I'm looking forward to being part of it."
Alton was at the Lane for six years after joining us as a trainee in 1997.
He made quite an impact after making his debut against Liveprool in November 2000 but injuries hampered his progress for the next two years.
He returned to reserve action in January but the realism of battling it out against the likes of Dean Richards, Ledley King, Anthony Gardner and Chris Perry for a centre-back spot has sunk in.
He added: "I loved my time at Tottenham and of course I would have liked to have stayed and play first team football in the Premiership.
"I was out for a long time, came back, was hopeful I'd get another contract and prove myself but it hasn't worked out that way.
"I needed to get out there and get some first team experience. Hull have handed me that opportunity and I'm looking forward to it."
Ex-Spur and former England U21 manager Peter Taylor is in charge of the Tigers who have been installed as early favourites for promotion next season.
They play in the new Kingston Communications Stadium where attendances didn't dip under 13,000 from Christmas last season.
"The club is in the Third Division but definitely going places," insisted Alton. "I went to the ground, met Peter Taylor, saw the set up and it is geared for First Division football.
"It is a fantastic stadium, 24,000 capacity and they get the support. If the club does well, the crowds will come.
"It's a football-mad city and they've already had well over 10,000 in there in the Third Division. I can't wait to get started."
Alton Thelwell admits he's just made the biggest decision of his life.