HMS Trenchant breaks through a metre of ice in the Arctic in a show of Britain's military strength.
The Royal Navy submarine is taking part in Ice Exercise 18, a major operation in conjunction with US forces.
It is the first time in a decade a Navy submarine has practiced beneath the ice amid increasing tensions with Russia.
The Arctic region has become an increasing focus of competition.
Russia is believed to hide its ballistic missile submarines there while NATO nations are developing skills to locate and destroy them.
It comes as Britain is braced for a reaction to Theresa May's decision to expel 23 diplomats.
A tit-for-tat reaction is expected and Moscow is also plotting a response to the United States after Donald Trump's administration imposed sanctions on Russians allegedly involved in interfering with the 2016 US elections and cyber-attacks.