The couple have snapped up the mansion near Kensington Palace - just down the road from Wills and Kate - and were impressed with the boosted security it offered.
"Security is a concern and the new house has a soundproof panic room," a source told The Mirror.
"It may sound over-the-top but they are actually the norm in Los Angeles."
Their new gaff also boasts seven bedrooms, five bathrooms, an underground spa, restaurant-quality kitchen, indoor cinema, library, underground car park and 'staffed massage rooms'.
The couple sold their previous UK base - nicknamed Beckingham Palace - for £9.5m last month, having been living in rented accommodation since returning home from the US earlier this year.
Victoria's also been splashing the cash on new offices for her growing fashion business.
It has also been rumoured that she is set to open a London store, telling the magazine in August: "I am looking into retail too, the e-commerce has been going really well. I get bored easily, so it's time for something new. London is where I want to have my first store."