Mark Sedwill: Cabinet secretary and top civil servant to step down in September

The most senior civil servant in Boris Johnson's government, Sir Mark Sedwill, is to stand down as cabinet secretary and national security adviser in September, Downing Street has announced.

Sedwill will be replaced as national security adviser by David Frost, currently serving as Mr Johnson's chief negotiator in talks on the post-Brexit trade and security relationship with the EU.

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