Gallagher Security names Siler to lead SMB & perimeter
Tue, 14th Apr 2026
Gallagher Security has appointed Tom Siler as National SMB & Perimeter Manager in Australia and added Tony Theissen and Alex Rajak in regional roles across New South Wales and the Australian Capital Territory.
Siler takes up the national post after serving as Enterprise Business Manager for the Victorian and Tasmanian sales team. Theissen joins as Business Development Manager for New South Wales, while Rajak has been appointed Technical Account Manager for the ACT.
The appointments expand Gallagher Security's sales and leadership structure in Australia as it increases investment in management and sales roles. They cover one national position and two market-focused roles in NSW and the ACT.
Scott Johnstone, Director of Sales - Australia, said Siler's appointment reflects the company's focus on internal promotion and national coordination.
"During his time with Gallagher, Tom has built a strong reputation for customer focus and market insight. His understanding of SMB and perimeter, combined with his experience working closely with regional teams, positions him well to lead these nationally important portfolios.
"His role will centre on providing clear leadership and alignment across regions, working closely with teams to support sustainable growth and ensure we continue to deliver strong outcomes for customers and partners as this part of the business scales.
"Tom is a great fit for the role given his depth of experience and balanced approach to leadership, which positions him well to support both our End Users and Channel Partners," Johnstone said.
Siler said he would focus on consistency across Gallagher's Australian operations and support for partners and end users.
"Gallagher has a commitment to developing leaders from within, and I'm excited to step into this national role. My focus will be on supporting our teams and partners, strengthening consistency across regions, and ensuring we continue to deliver excellent results for End Users," Siler said.
Regional hires
In New South Wales, Theissen joins with more than 35 years of experience in the security and technology sector. His background includes technical delivery, leadership, and enterprise sales, with a focus on large integrated projects.
David Issa, State Manager - NSW and ACT, said Theissen's experience would support the company's regional sales effort.
"Tony's background spans technical delivery, leadership and enterprise sales, with a strong track record in driving strategic growth, particularly in delivering large-scale integrated solutions," Issa said.
Rajak brings 20 years of industry experience to the ACT role. His background includes work in Federal Government and Defence settings, as well as technical delivery, project management, solution design, and bid management.
Issa said Rajak's experience would support customers and channel partners in the territory.
"Alex's background spans technical delivery, project management, solution design and bid management, with strong expertise in stakeholder engagement. His wealth of knowledge will be an asset to End Users and Channel Partners across the region.
"Strengthening our national presence goes hand in hand with investing in leadership capability, ensuring we deliver consistent outcomes for our End Users and Channel Partners while supporting continued growth across Australia. We are thrilled to welcome Tom, Tony, and Alex to Gallagher," Issa said.
The appointments reflect a dual focus for Gallagher in Australia: tighter national oversight in the SMB and perimeter segment, and stronger commercial and technical coverage in two eastern jurisdictions. They also continue a mix of internal promotion and external recruitment for senior roles.
The announcement focused on the new management structure and the experience the three appointees bring to Gallagher's Australian operation.