Upton is currently commercial director of specialist mortgages.
The move stems from David Alcock, managing director of development finance at HTB, deciding to bring in another senior executive to help him manage the division as his deputy.
Alcock said: “Alex Upton has made an important contribution to the successful development of the specialist mortgages division which, under the able leadership of Charles McDowell, is now the largest single business within HTB.
“Alex’s skills and capability will be invaluable in helping me to manage and channel the structural growth we are driving in our development finance portfolio.”
Upton added: “I’m keen to broaden my experience and this is an exciting opportunity to help David scale up his business.
“Specialist Mortgages now has a team of very able people and my move will create the space for some of those people to take on new responsibilities.”
Matthew Wyles, chief executive of HTB, said: “Talent is the most potent single ingredient in HTB’s proven formula.
“I have committed to developing capable, ambitious people by giving them exposure to different facets of the bank’s activities.
“This approach has the added benefit of bringing fresh new ideas advanced by people with a proven track record of achievement. I congratulate Alex as she begins this exciting new chapter in her career.”