The Daily Telegraph has a story about a church in London which has been hosting an Islamic prayer service. There are more details here, presumably written by the person who shot the video.
First point: do not believe everything that you read (or see or hear!) in the newspapers (I speak with authority).
That being said, unless the video is demonstrated to be a forgery, I think this is a serious breach of ordination vows – specifically the declaration made at ordination and then repeated at each new appointment that “in public prayer and administration of the sacraments, I will use only the forms of service which are authorized or allowed by Canon”. I believe that there are other elements of Canon Law that are relevant.
I believe that our words matter, and when ‘Allahu Akhbar’ is chanted in a church, then this is a quite straightforward example of blasphemy – it is a profaning of Christian worship – and sacrilege – a profaning of the place of Christian worship. To argue otherwise is to indulge in syncretistic nonsense of the worst sort. The different faiths, whilst they have all sorts of family resemblances, are not simply different paths up the same mountain. It matters that Jesus was crucified, and to preach Christ crucified is to say that Jesus was killed, which the Koran explicitly denies.
I can see all sorts of arguments for pursuing peace, hospitality and friendly co-operation with those of non-Christian faiths and no faith at all. What I cannot see an argument for is abandoning our own distinctive identity, with all that binds it together.