The London Stock Exchange, which last week upgraded its electronic trading platform, has suffered its first major systems problem in seven years, leaving brokers unable to trade on the exchange's Sets order book for 45 minutes around the close of the London market today.

The exchange was forced to extend its closing auction from 16:30GMT to 18:00GMT to give customers time to trade out their positions and report them back to clients, after brokers were left with no live pricing data for 45 minutes.