Edwin Thomas
Martin Jerrold, a lieutenant in the British Navy in the early 1800s, in the Reluctant Adventures trilogy:

The Blighted Cliffs (2003)

The Chains of Albion (2004)

Treason’s River (2006)

Written as Tom Harper
Demetrios Askiates, a former bounty hunter and bodyguard, in service to the Byzantine Emperor in late 11th century Constantinople, in the First Crusade trilogy:

The Mosaic of Shadows (2004)

Knights of the Cross (2005)

Siege of Heaven (2006)

Written as Tom Harper

The Lost Temple (2007)

The Book of Secrets (2009)

The Lazarus Vault (2010)

Catacomb (2011)

Secrets of the Dead (2011)

The Orpheus Descent (2013)

Zodiac Station (2014)

Black River (2015)