Put it off long enough.

New Thatcher:

After Thatcher's death Harry managed to salvage the remains of his personality core. However upon inserting his core back in, he went into a frenzy hurting many of the Scotland yard mechanics, and ran off.

Harry suspected it was probably a last instinct of survival, since Baronet's betrayal did come quite sudden.

Whereabouts:

He is with the House of Griffiths under Valeta's supervision.

The Griffiths House has been around for a long time, but not as long as the Targaryen's and such. They were around since the 1800's and made a lot of success of merchandise.
Their products soon into more advanced technology, and now with Valeta head of the house she hopes to make her own Scotland Yard to be more clear.

When she found Thatcher she was quick to take him, and to befriend him.
Although she has quite a few knights of her own, they all lack compassion or independent thinking. She views them as tools more so than actual people.

-bloodhound-