In a quandary and after some advice....

On the 6th April 2013, new tenant's moved into our rental. They signed a 12 month tenancy agreement.

Do to breakdown in our relationship - husband is now needing to move back into that property.

Is there any way this can happen? I've seen people mention section 21 of the H.A - but what do we/I have to do to go down this route?

thanks!