The possibility of one of the London Stock Exchange's arch-rivals becoming a partner in the exchange's new dark pool trading system moved a step closer yesterday after a banker close to the process said getting the buiness up and running is now a priority.

The move centres on Baikal, a trading system set up by the LSE and Lehman Brothers WHEN. Lehman Borthers in Europe has since been acquired by Nomura, which owns a similar system called Chi-X. Sine being set up WHEN, Chi-X has been winning market share from the LSE, and on its most successful days has traded as much as HOW MUCH of the LSE's volumes.