Paul Nicholls' chaser put the finishing touches to his preparations for the Cheltenham Gold Cup with a fifth victory on the spin.

But in almost the exact same circumstances to the King George VI Chase on St Stephen's Day, his supporters were put through the mill after Ruby Walsh's mount clattered the final obstacle.

Kauto Star had previously gone about his business with the minimum of fuss and ghosted past Royal Auclair to take the lead two out.

However, the seven-yearold's bad error let L'Ami into the contest and a rare battle ensued towards the line, with the 2-9 favourite digging deepest to prevail in a thriller.

"We were just starting to race at it (the last fence) and he didn't do one thing or the other, " Walsh told Channel 4 Racing afterwards.

"He was just too keen all the way today, he never switched off. But the way he battled back, he'll get the trip in the Gold Cup."

Nicholls was pleased to come through but was understandably concerned: "It's frustrating really because he jumped absolutely brilliantly - foot-perfect -- but just stepped at the last.

"But Ruby said he'll definitely get the Gold Cup trip.

"It is frustrating though, because he has got a good jump in him. It's in the lap of the Gods, but he'll improve on that."

Francois Doumen was quietly confident that L'Ami would also improve: "I am still conscious that there was a 10lb difference between them, but Cheltenham will be a fair race, not a sprint.

"I have a lot of respect for the opposition, but it was not a bad way to approach the Gold Cup and it gives us some hope."

Trainer David Pipe was all smiles 35 minutes after the demise of Acambo in the totesport Trophy later in the day when Well Chief made a mockery of a 22-month absence to win the totepool Game Spirit Chase.

Timmy Murphy's mount, last seen defeating Azertyuiop at Sandown in December 2005, brushed past long-time leader Ashley Brook three from home and never looked back.

The 5-2 shot extended his lead without breaking into sweat and stormed to an emphatic 11-length win from the front-running Ashley Brook.

But the Grade Two heat lost some of its lustre when last season's Arkle winner Voy Por Ustedes fell early in the race.

"It was great, " said Murphy. "The plan was just to get him back and keep things nice and simple. He's a very good horse and fingers crossed he stays in one piece."

"I thought he was fit enough to do himself justice and he's had a good blow afterwards, " Pipe said.

"David Johnson allowed us to take our time with him and he was superb.

"I wanted to give him a race before Cheltenham because he's a buzzy horse and was keen over the first three or four fences."

Earlier in the day, Heathcote caused a 50-1 shock in a typically-frenetic renewal of the totesport Trophy.

A clutch of runners unsurprisingly held a live chance in the Berkshire cavalry charge as Pedrobob and Papini temporarily gained the initiative two flights from home.

Gary Moore's charge, ridden by the trainer's son, Jamie, was always in a handy position and saw a glimmer of daylight between himself and the chasing pack after the last.

Heathcote stayed on impressively from there and belied his huge odds to fend off Overstrand's rattling late surge and score by a neck.

Pedrobob was third, two lengths further in arrears, while Caracciola was fourth.

Disappointments of the race were market leaders Tarlac and Acambo, who never seriously threatened at any stage, with the latter pulled up after dropping right out of it in the straight.

A delighted Jamie Moore said: "He's only small but he goes in soft ground and that was probably one of the big factors. I probably got there too soon but he was going so well."