Chopra is on seven-under-par 135 after firing a bogey-free 65 with Australia's Andrew Dodt and China's Liang Wenchong two shots further back.

CNN: Chopra leading rain-hit tournament

Montgomerie was suddenly one over par and seven adrift of Siem and Australian Andrew Dodt at that stage before dropping from 14th to 47th by taking a shocking 42 to the turn and handing in a 76.

BBC: Gallacher posts course record 63 at Celtic Manor