Absolutely not.  If your right to light was gained via the Prescription Act 1832 (20 years continuous enjoyment), you will lose it if it is blocked for 12 months.  Therefore, you must assert your rights immediately.  If matters were to end up in Court, actions of both parties to the dispute will be closely looked at.  Thus, if you remained silent, and did nothing to assert your legal rights until for example, the works had progressed, you may find it harder to get an injunction than if you had raised the subject before the neighbour made a commitment to their scheme.  Courts like to see parties playing ‘fair’.  If they feel you raised a matter ‘too late in the day’, they may consider it would be oppressive to the developer to grant an injunction.  So, if you have concerns – make them known.