Englishman

"Only contacts are the messages I receive from The Englishman." "'The Englishman'? Your Handler? How do you know he's English?" "The way he refers to certain things. He uses 'lift' instead of 'elevator', 'boot' instead of 'trunk'." "Think about the messages. What else do you know about him?" "He's late 30s, early 40s. Uses dated references-- 'disk drive' instead of 'flash drive', 'Burma' instead of 'Myanmar'."

- Akela Amador and Phil Coulson

"The Englishman" (as Akela Amador referred to him), real name unknown, was a former member of MI6 who was later forced into working for HYDRA.

Biography
"The Englishman" was a former agent of MI6 of English nationality that fell off the grid several years before being located by Phil Coulson.

Through unknown circumstances, he was coerced into HYDRA's service. They installed a Backscatter X-Ray Eye Implant into his head to monitor his movements and ensure his loyalty via a remote-controlled kill-switch.

One of his duties for the Centipede Group was to act as "handler" to field asset Akela Amador, who was also installed with the eye implant. The Englishman would give Amador what she needed to know and do for her assignments, while at the same time monitoring her movements to ensure her loyalty. His actions and, indirectly, Akela's actions were in turn monitored by HYDRA. It was while monitoring one of Amador's missions that his transmissions were detected by a S.H.I.E.L.D. team led by agent Phil Coulson.

Coulson's team managed to bring Amador into custody and remove her implant before The Englishman could activate her kill-switch. Upon fleeing the location, The Englishman was confronted by Agent Coulson, whereupon his own implant's kill-switch was activated, killing him instantly.

Trivia

 * The Englishman was equipped with the same Backscatter X-Ray Eye Implant as Akela Amador,  Brian Hayward and Michael Peterson.