Once considered one of the hottest properties in football, the tall striker is looking forward to testing himself against the rest of the Premiership.
Speaking to the official site he said, "I am really happy to be at West Ham. They are a big club and
I want to show the fans that I can score goals and help the team to go up the league. I am excited to be here."
Tristan has been training with the club for the last two weeks and has obviously done enough to impress Gianfranco Zola. "The manager has spent lots of time working with me," he said.
"He has helped me a lot and I want to say thanks to him by scoring lots of goals and doing well for the club. I am very grateful to the manager for giving me the opportunity to play here.
"I have been really impressed from the moment I arrived at the training ground. The coaching staff and the players have all helped me to settle in. I had a lot of offers to go to other countries and play for a lot of money but I feel that I still have lots to offer and I want to show West Ham fans that I can still play at the highest level. That is why I am here."