Complex sentence: However permission was refused and it was said to be inconsiderate as Manchester was still rebuilding from the Blitz in World War II, had it been built, it would have been not only Manchester's tallest building, but the tallest in Europe.
Split into simpler sentences: However permission was refused and it was said to be inconsiderate as Manchester was still rebuilding from the Blitz during the Second World War. Had it been built, it would have been not only Manchester's tallest building, but the tallest in Europe.