LONDON, Dec 17 - The dollar spiked a third of a yen higher to 107.80 yen in a matter of minutes on Wednesday with dealers wary of Japanese intervention but uncertain whether the Bank of Japan had actually been active. "It looks like the BOJ, but it certainly didn't come through us," said one trader at a Japanese bank in London. Others were sceptical of whether the central bank had driven the move although they thought the bank had been in the market during the session guiding the dollar/yen price. "It's not intervention. There was a little bit of a helping hand but the bulk of the move was driven by (a European bank)," said another trader at a Japanese bank in London. "Tokyo names have been around buying dollar/yen at the lower levels most of the morning which would indicate there is some sort of smoothing going on but the move up in dollar/yen is not largely intervention. It's a commercial order," the trader said. By 1020 GMT the dollar was slightly higher on the day at 107.60 yen, having made the rapid jump from 107.40 to 107.80. It remains around one yen above a three-year low set last week.//