Waheed Ali, said Tanweer played cricket with him on the evening of July 6, 2005.
He said: "On that day he made a bit more of an effort, looking back."
The pair, who both lived in Beeston and were once very close, saw less of each other as Tanweer spent more time with July 7 ringleader Mohammed Siddique Khan, Kingston Crown Court heard.
But Ali, 25, said his friend gave him no clue what was planned. He said he told him they were "doing something for the brothers" and asked Ali to stay away.
But Ali said on July 6 he was happy his friend had come to talk to him and thought things were getting back to normal.
"This was the last time I saw my best friend alive and I wouldn't change that for all the tea in China.
"I think he knew that this was the last time he was going to see me. It's difficult because he had been my friend since I was little and I had a lot of love for him. But what he did was unbelievable."
Ali is charged, with Mohammed Shakil, 31, and Sadeer Saleem, 27, all from Beeston, Leeds, with conspiring with Khan, Shehzad Tanweer, Jermaine Lindsay, Hasib Hussain and others unknown, to cause explosions between November 17, 2004 and July 8, 2005. They all deny the charges.
Proceeding