Pruning (or worse) a Myrtle Communis

Hi

I hope someone can help with my problem.  I have just bought a 200 year old house, called Myrtle Cottage.  Its had this name for while (carved on the gatepost) and known as such in local history records going back to the mid 1840s at least. 
It has a large (approx 15 foot tall by 10 feet wide) Myrtle Communis by the front door which is obviously thriving (sheltered south facing position), but its just too large and blocking light into the front dining room window and I would like to reduce its size, whilst not killing it or making it look terribly ugly.

I don't know how long Myrtle's may live, but I'm sensitive to the fact that it may be the original Myrtle after which the cottage is named, and would prefer not to remove it.  Would it manage a fairly serious prune/cut back?  Without wanting to incur the wrath of the local history community I would be happy to remove it and plant another smaller one in its place if it was the only answer.

Any thoughts welcome.
Thanks

My experience of this plant is that it is not a fast grower but is expected to reach up to 3 metres. Thinking of the height of your plant it may very well be the original. Probably time to ask the experts.Try contacting www.jekkasherbfarm.com for their opinion. This is the business of one Jekka McVicar, the' Queen of Herbs' according to Jamie Oliver. Jekka has run for many years an organic herb business outside Bristol. She has won more Chelsea golds for her herbs than anyone else I can think of.

You could also try the Royal Horticultural Society www.rhs.org.uk but you might have to be a member for individual advice.

There is also the National Herb Society which is situated outside of Banbury in Oxon. Sorry don't have the website details to hand.

If all else fails, try contacting your local Horticultural association, better still join it and make new gardening friends.