Do not expect umpires to over-rule their colleagues too often when contentious decisions are referred to them during the Friends Provident Trophy.

Teams are allowed two per innings under an ICC-supported experiment being trialled in the 50-overs competition this season in televised games only.

Sussex skipper Chris Adams was the first player to use it at Taunton yesterday, when he referred Jeremy Lloyd's decision to give him out leg before in the 15th over.

TV umpire Barrie Leadbeater had made his mind up within 20 seconds but it was another two minutes before the decision was conveyed to Sky Sports and by then the Somerset crowd had begun a slow handclap.

Leadbeater, one of the most experienced umpires on the circuit, said: "We can only reverse a decision if the umpire has made a clear and obvious mistake. This wasn't the case and I'd be surprised if obvious mistakes are made by umpires."

On first glance it appeared there was doubt as to whether Peter Trego's delivery was too high and drifting down leg. But replays showed that it had straightened enough to hit middle and leg.

Alan Fordham, ECB's head of cricket operations, said the experiment might be widened to include other domestic competitions if it is a success. He said: "It could be looked at as being against the spirit of the game but we are looking to help umpires get more decisions right."

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