David Dickinson
Lord Francis Powerscourt, an ex-Indian army intelligence officer and Irish peer, working as an investigator in the late Victorian period, in England and elsewhere:

Goodnight Sweet Prince (2001)

Death and the Jubilee (2003)

Death of an Old Master (2004)

Death of a Chancellor (2005)

Death Called to the Bar (2006)

Death on the Nevsky Prospekt (2006)

Death on the Holy Mountain (2008)

Death of a Pilgrim (2009)

Death of a Wine Merchant (2010)

Death in a Scarlet Coat (2011)

Death at the Jesus Hospital (2012)

Death of an Elgin Marble (2014)

Death Comes to the Ballets Russes (2015)

Death Comes to Lynchester Close (2016) [US due May 2, 2017]

Death at Melrose Hall (UK due March 2, 2017)

Mycroft Holmes pastiches:

The Mycroft Holmes Casebook (2014) [ebook novellas & SS]

The Mycroft Holmes Omnibus (2014) [ebook, selection from Casebook)