Note- we have figured out the code- it's pretty simple- the alphabet offset so that A becomes B and B becomes C etc. It couldn't have fooled Hilda's parents and the war officials too much but I'm sure his tiny handwriting did. Just to make things a little trickier, Rothwell has transposed the code too for some of the words. You definately need a sheet of paper and a pencil for them!
Efbsftu is Dearest and Ebsmjoh is Darling
J. tfou ufmfhsbn I sent telegram
Efbsftu, J bn ufssjcmz mpofmz apx, Cvu xf tibm hfu pwfs ju. Dearest, I am terribly lonely now, but we shal(l) get over it
Diffs vq Ebsmjoh. Cheer up Darling
J tbx uif cbdl pg zpo hpjoh gopn the cpupn I saw the back of you going from the botom (of Pesthouse)
My Efbsftu, My Dearest
My Ebsmjoh, mpwd & ljttft My Darling, love & kisses