So large it has its own location on googlemaps, bingmaps etc. This is the home of the wife of the mayor of Moscow, currently. It's being renovated to include all sorts of luxury. Witanhurst is the name of this historical Georgian-style mansion located on a 5 acre (20,000 m2) site estate in the village of Highgate, North London. It is the second-largest house in London in private ownership, the largest being Buckingham Palace.

Witanhurst house was built in between 1913 and 1920 for the soap manufacturer, Sir Arthur Crossfield MP.  He liked his luxurious parties, and Princesses Elizabeth and Margaret attended Tennis parties in the 30s. It has 65 rooms spread across three floors, including 25 bedrooms. One of the largest is the Grand Ballroom, measuring 70 feet (21 m) long with a height of 20 feet (6.1 m). It has oak flooring and the timber wall panels are in walnut, with carved cornices embellished with gold leaf.

On 16 July 2008 it was reported that Yelena Baturina, the wife of the Mayor of Moscow (Russia) and a billionaire in her own right, purchased the property for an estimated £50m (approximately $100MM USD.) The renovations are now under way with an estimated cost of 40 million. These include a swimming pool and 24 space car park under the front courtyard.

The three-pronged gatehouse sits out front, with the scaffold covered mansion behind.

Arriving to a misty dawn on Highgate Hill, TheSpaniard and I wandered to a pre-decided access point. As we wandered up to the Mansion, it towered above us, cctv cameras lurking to spot us, but failing.

We got into a room with a some shelving and wooden floors that was dark and uninteresting. Unsure if the house had people in, it was a bit nerve racking. As we moved into the next room, the thoughts of other people faded, to be replaced by jaw dropping. The room was a glorious wood lined room of luxury.

As we then went into the even entrance hall, we noticed the front door was wide open. Every corner involved careful creeping around. The entrance hall had amazing dark wood bannisters and panelling.

A welcoming fire to keep guests warm on their arrival

Around the next corner was a long corridor with a gorgeous inlaid ceiling

Through the door on the left was the main ballroom, where Fame Academy recordings were held for the BBC.

At the far end was a piano, but I resisted the lure of knocking out my rendition of The Entertainer (which sounds similar to a piano falling down stairs).

We climbed the main staircase, and walked along a hall. It suddenly seemed there was a lot of natural light flooding in, and a craning of our heads located the source.

It's hard to work out the most impressive bit about this place. Further on near some back stairs, we found this interesting mural. (Apologies for the quality, I was going through my experimental HDR phase).

Through loads of gutted bedrooms, we finally got up another floor into the eaves of the house, to find more empty rooms.

In another room, a window didn't have a frame, so we climbed out onto the roof. The windows with all their original wood being sanded down and re-treated.

From their it was a few steps up to the main roof, which was massive. And not only that, it was covered by a huge sheet of metal to form a protective roof to the work going on around us.

A quick pose with TheSpaniard, unable to keep his limbs still as we stood at the highest point of the house.

On the way down, I spotted the main balcony, that overlooks a sort of Grecian garden. It seemed right at this point to spark up a joint, although I'm pretty sure a lot harder narcotics have been used in this place over the years.

I thought we'd done with the main part of the house, when I noticed some stairs going down to a basement. There were work jackets here and a digger, so we were extra careful of people being about.

The basements were huge and the same size as the floor of the house.

We then went back up and looked at the servants wing, which was pretty dull and full of uniform size rooms that were all stripped. Signs on a wall pointed to this being used as a film set for 'Jane Eyre'.

We went out to the garden via the long route, didn't want to appear on cctv thanks. There was the pavillion, not looking in too good a condition.

And with that we left, me clumsily tearing a small hole in my lovely gore-tex coat. D'oh! We wandered up to Hampstead Village for a slap-up breakfast and cup of tea. Then TheSpaniard left for his siesta!

Cheers to Scott Badman for the tip off.