The Londoner, who had a trio of eagle threes in what he described as an "up and down round", is one shot clear of the Spaniard, Ignacio Garrido, and two ahead of Costantino Rocca, the Welshman, Phillip Price, and Jose Rivero.
Colin Montgomerie (70), Seve Ballesteros (70), Bernhard Langer (71), Jose-Maria Olazabal (73) and Ian Woosnam (75) are lagging behind, with Olazabal and Woosnam needing good second rounds to make the cut.
Ballesteros, Olazabal and Montgomerie, with strong backing from Nick Faldo in the United States, have condemned the European Tour as having too many players and lacking quality. But Mitchell, who finished 18th in the Order of Merit last year and in the top 28 in three of the last four seasons, does not agree.
"Everybody has their own point of view," he said. "It's OK for the superstars to say what they like. They have no worries. But there are guys out there who have no money, no sponsorship. It can cost them a grand a week just to play and it's a different ball game at that level.
"Those players who have got millions and get exemptions all over the world can do what they want to do. They are not going to struggle. "We would have a great tour if all the top players played over here," he said .
Mitchell, was much happier to talk about his fine round. His three eagles came at the 507-yard fourth, where he holed out from a green-side bunker, the 538-yard seventh, where he hit his second shot to five feet with a seven-iron, and the 477-yard 12th, where he was on the green in two and holed out from eight feet.
As he also chipped in from 25 feet for a birdie at the eighth it was quite a day but Mitchell said he was not sure if three eagles was his best-ever tally.
"I thought I had four when I won the Austrian Open in 1992 but it may have been just three," he said. "Certainly this is not the first time I have done it."Reuse content