(Adds CEO comments, details, background, shares)
By Arathy S Nair
March 16 (Reuters) - British lender OneSavings Bank Plc reported a 15.7 percent growth in its loan book in 2016, largely in line with expectations, and said it estimated net loan book growth in the mid-teens this year.
Chief Executive Andy Golding expressed optimism about the UK economy, but cautioned that uncertainty loomed over Britain's departure from the European Union as divorce talks get set to begin.
Shares of the company rose as much as 4.1 percent in morning trading on the London Stock Exchange to hit a record high of 436 pence.
"We have got Brexit looming and the triggering of Article 50 and nobody really knows what impact that's going to have on the UK macro economy, although the economy seems to be very very well at the moment," Golding told Reuters.
Brexit minister David Davis said on Wednesday he expected legislation giving Prime Minister Theresa May the power to trigger Article 50 of the EU's Lisbon Treaty, launching divorce talks, would be formally approved by Queen Elizabeth on Thursday.
OneSavings, one of the banks aiming to challenge Britain's "Big 5" lenders, said in August that it had increased its focus on professional landlords and tightened lending criteria for financing smaller residential developments after Britain voted to leave the European Union.
Golding said the lender's core markets and its biggest market, professional landlord segment, were operating "exceptionally well."
The lender said net loans and advances grew to 5.94 billion pounds ($7.30 billion) in the year ended Dec. 31 from 5.13 billion pounds in 2015.
Analysts on average were expecting loans and advances of 5.95 billion pounds, according to a company-compiled consensus.
OneSavings, based in the southern British county of Kent, said underlying pretax profit jumped 29.4 percent to 137 million pounds, well ahead of the company-compiled consensus of 131.9 million pounds.
Earlier this month, smaller rival Aldermore Group Plc forecast strong loan-book growth in 2017, and said Britain's planned exit from the EU was unlikely to have any material impact on its business this year.
OneSavings said it kicked off 2017 with a fully loaded common equity tier 1 ratio of 13.3 percent and said it expected to maintain it at a minimum of 12 percent.
The stock was largely flat at 419 pence at 0910 GMT. They had risen about 65 percent in the past 12 months as of its close on Wednesday. ($1 = 0.8141 pounds) (Reporting by Arathy S Nair in Bengaluru; Editing by Amrutha Gayathri)