According the Mike Smith (the DC5's lead singer and keyboardist), Dave Clark was looking for a lead guitarist and asked Mike if he knew anybody. Mike recommended Lenny saying there was no one better. Mike and Lenny had worked together in a previous band.
He was one of four members of the group who wrote songs. He co-wrote, with Dave Clark, their 1965 hit "Catch Us If You Can," and contributed 5 more tunes on the "Having A Wild Weekend" soundtrack album. He also contributed "Crying Over You" and "When" to their 1965 "Coast to Coast" album, and sang lead on the 1968 hit "Everybody Knows" which reached number 2 on the British charts.