The head of Britain's Secret Intelligence Service, the foreign spy service known as MI6, will warn that Russia poses an "aggressive, expansionist, and revisionist" threat, in her first speech since taking office.

Blaise Metreweli took over from Richard Moore in October, becoming the first female chief of MI6 — a role publicly known by the codename C — in its 116-year history.

"(Vladimir) Putin should be in no doubt: Our support is enduring. The pressure we apply on Ukraine's behalf will be sustained," Metreweli will say on Monday, according to advance extracts of her remarks.

"The export of chaos is a feature, not a bug, in the Russian approach to international engagement, and we should be ready for this to continue until Putin is forced to change his calculus."

Britain has sanctioned several Russian business figures, political leaders, companies, ships, and entities, including the entire GRU military intelligence agency, since Russia's invasion of Ukraine in 2022.

Over the weekend, Germany hosted U.S. and Ukrainian delegations for talks on a ceasefire deal, before a summit in Berlin on Monday that will include European leaders.

Metreweli will also highlight the need to ramp up the use of technology to tackle threats to U.K. security, including terrorism and information warfare.

"Mastery of technology must infuse everything we do. Not just in our labs, but in the field, in our tradecraft, and even more importantly, in the mindset of every officer. We must be as comfortable with lines of code as we are with human sources, as fluent in Python as we are in multiple languages," she will say.

Air Chief Marshal Richard Knighton, head of Britain's armed forces, will also call in a separate speech on Monday for a "whole society" approach to defense in the face of growing uncertainty and threats, and highlight an increased probability of Russia invading a NATO country.