* RBC accounted for 78 pct of HBC buy orders on Tuesday
* HBC shares fell on Tuesday, firmed on Wednesday
TORONTO, Nov 21 (Reuters) - Data for the first day of preliminary trading since Canadian retailer Hudson's Bay Co returned to public markets, Tuesday, showed that Royal Bank of Canada - HBC's lead underwriter - accounted for a whopping 78 percent of buy orders for the shares.
It's not clear if RBC was buying on its own behalf to prop up the share price, or whether its brokerage unit was acting on behalf of clients. RBC declined to comment.
Shares in the storied Canadian department store operator had a disappointing debut on the Toronto Stock Exchange on Tuesday, falling as much as 3.5 percent before ending the day 1.5 percent lower at C$16.75.
HBC priced the offering of about 21.5 million shares at C$17 apiece - at the bottom of an already lowered range of C$17 to C$18. The company, which controls retailer Lord & Taylor in the United States and Hudson's Bay stores in Canada, had originally targeted a price of C$18.50 to C$21.50 a share.
The Toronto Stock Exchange data for Tuesday shows RBC Capital Markets executed some 3.5 million buy orders for the shares, or more than 78 percent of the volume, buying shares at an average price of C$16.85.
RBC also accounted for just under 1.1 million sell orders for the stock at an average price of C$16.84.
HBC shares dipped lower for much of Wednesday, amid thinner trading volumes, but the stock rallied late in the day to close at C$16.90. In trading on Wednesday, RBC accounted for nearly 55 percent of the buy orders placed for the stock. Shares in HBC are trading on a "when-issued" basis ahead of the offering's official Nov. 26 close. All trades in the stock executed ahead of the official close have to be matched and settled, as and when the offering closes.