Jackpotjoy began life on the London Stock Exchange as its shares shifted across from Canada.
The online bingo and casinos operator, fronted by Dame Barbara Windsor, did not raise any money but it is the first main market float of the year. It traded up slightly at 610p, giving it a market value of £450 million.
On AIM, radiation detection firm Kromek, which was spun out of Durham University, rose 0.48p to 20.35p after raising £21 million to bolster the balance sheet.