Swan Yamaha's Tommy Hill lost his lead in the MCE British Superbike Championship following a difficult introduction to the Showdown stage of the series at Assen.

Hill was involved in a bizarre incident in race one, when the current champion was knocked off his machine as he returned to the grid following the sighting lap.

It appears as though a mechanic ran into Hill's machine, jamming the brake lever and sending him over the handlebars.

He started the race from pit lane but was later forced to retire his stricken Yamaha.

Hill, who finished fourth in race two after being passed by Alex Lowes on the final lap, has slipped to third position in the standings and is now 22 points behind Tyco Suzuki's Josh Brookes with two rounds remaining.

"It has been a difficult weekend," Hill said.

"I was coming through the back of the grid in race one and it was pretty busy and a mechanic from another team didn't realise I was there and ran into me and it jammed the brake lever on.

"I went over the bars there was nothing that I could do about it. The bike went down, but the team did a great job to do a quick fix and get me out there," he added.

"In the second race I knew I needed to score the points after the retirement in race one and I got up to speed and was pushing hard and got up to third but Shakey and Josh had got away a bit.

"I thought I could pull them in but then Alex (Lowes) put in a bit of a harsh move and that put me fourth.

"We now need to go to Silverstone and get back on the top step of the podium to get those points back in the standings."