How did Lenny McLean die?

It was during the filming of guy Richie's "lock stock and two smoking barrels that McLean was struck ill by what was believed to be the flu. However, upon examination it was found he was suffering from lung cancer which had spread to his brain. He died shortly afterward, in July '88 in London just weeks prior to the release of the film. Richie dedicated the film to him and had billboards for the film changed to feature McLean in tribute.