Specialist British bank Shawbrook made a stunning stock market debut on Wednesday in London with shares rallying to 305p, well above the top of its preset price range of 290p.Shawbrook is seen as a new breed of British bank entering a market dominated by big institutions like Royal Bank of Scotland and Barclays.The floatation comprises 75,000,000 ordinary shares, representing 30% of the company's ordinary shares that will be in issue at admission. It gives the company a market capitalisation of £725m.It is expected to raise gross proceeds of approximately £90m for Shawbrook. Bank of America Merrill Lynch and Goldman Sachs were appointed to handle the initial public offer."Our focus remains on providing UK customers with a fresh, pragmatic approach to lending and savings whilst driving further growth by maximising opportunities in existing markets, capitalising on the embedded growth in our current loan book and developing a range of products to facilitate expansion into adjacent segments," said Richard Pyman, chief executive of Shawbrook.Pyman added that Shawbrook continues to deliver on its strategy to "become an increasingly well-known name in the specialist world of British banking."Last month, challenger bank and specialist lender Aldermore, a similar business to Shawbrook raised £75m in a successful IPO, which triggered a rally in the stock price.