Hi @shadmantabib -- we are looking into this, I apologise that it is taking some time, but I do not have the authority to draft such a letter without taking advice, which I am doing as fast as possible.
We are looking into this for you. I am sorry that this hackathon is taking place over a relatively short timeframe and we do not currently have a formal process for issuing such letters. I will get back to you as soon as I possibly can.
Dear @shadmantabib and @NiloyKumarMondal -- we are looking into this now. We asked the UK Foreign Office for help on this but at this point have not received a response. I will reply later with further information when I have it -- Pete