Long before Huawei was a diplomatic headache for the British government, it was a commercial problem for Cisco Systems.

For decades, the Silicon Valley stalwart has been the 800-pound gorilla of a lucrative global market for internet switches and routers – critical pieces of kit which help households and businesses connect to the internet.

When the Chinese company made a foray into the sector in the early 2000s, a fierce legal dispute erupted as Cisco sought to defend its position.

Cisco – which in 2018 controlled a 51pc share of the $44bn (£33.9bn) market according to figures from Synergy Research – launched a lawsuit claiming Huawei had pinched some of its technology.

Some of the alleged abuses were so blatant that spelling errors in Cisco manuals had also featured in Huawei’s.

Either way, after years of legal rumblings, a settlement and a non-compete agreement was struck, which forced Huawei to retreat.

Now – after its high profile battle over 5G – Huawei is preparing to open up a new front in an increasingly bitter fight between the US and China for control of the future of the internet – by making a concerted push into the router market. It is a move with huge implications. The new push poses not just a big threat to Cisco and other Western companies but is fuelling fresh fears over potential espionage.