The Time Travellers by Simon Guerrier

The TARDIS has returned to London, but this isn't the city Ian and Barbara remember. Torn by war, the city of London is in ruins and it appears they have arrived amid a war.

A war that the British are losing.

With his friends mistaken for vagrants and sentenced to death, the Doctor is press-ganged into helping perfect a weapon that might just turn the tables in the war. The British Army has discovered time travel. And the consequences are already devastating.

What has happened to the world that Ian and Barbara once knew? How much of the experiment do the Doctor and Susan really understand? And, despite all the Doctor has said to the contrary, is it actually possible to change history?