Cheetham was a key member of the research team at University College London (UCL) in the United Kingdom, working under Professor Peter Kirstein, a pivotal figure in the development of the internet outside the United States. In the early 1970s, UCL was selected to establish the first international node of the ARPANET.
As an engineer and system administrator, Cheetham played a crucial role in setting up and maintaining the technical infrastructure required for this groundbreaking connection. His work involved configuring and managing the Interface Message Processor (IMP) at UCL, which acted as the gateway to the ARPANET. In November 1973, under his technical guidance and that of the UCL team, the first successful ARPANET link between UCL and the United States (specifically, Bolt Beranek and Newman (BBN) in Cambridge, Massachusetts) was established.
This international connection was a momentous step, demonstrating the global potential of packet-switching networks and transforming ARPANET from a domestic U.S. network into an international one. Cheetham's technical expertise and efforts were instrumental in bridging the transatlantic gap and laying fundamental groundwork for the internet's eventual worldwide growth and adoption.