This letter has surfaced for the need of expressing my heartfelt apologies for not joining your construction company even after applying for the job and getting the job application approved. Certain unfortunate events have cropped up on the personal front of mine and these have denied me to assume the job of civil engineer in your esteemed construction firm. This is more of a grim loss to me than to the firm and I regret the occurrence of these unfortunate circumstances.
I wish to take this moment to inform you that any further opportunity to get associated with an esteemed construction firm like yours would be welcomed on my part and I would serve for the best in future. The present context of events suggests that we do not work together and I wish that may the future bring in the best for both the sides. Apologising for the not joining,