We are slowly renovating our 400 year old stone built house but the OH needs some advice. We are turning the stables into our lounge and we need to install a window. How do you go about making an opening through two foot wide of stones without the whole wall falling down? All the stones are of irregular shape and size. If anyone has any experience, or advice, it would be gratefully received.

using akro rods and 4x2 timber beams?

Mark out on the wall where you want the window opening to be. Then mark above that for the new lintels, precast concrete best but heavy. The lintels need to be at least 150mm wider than the window opening on either side. If the wall is two ft thick, that´s 600mm, so you´re going to need at least 3 lintels, one behind the other. Then you need to knock through 2 or more holes (depending on how wide your new opening is going to be) above the top of the lintel level. Insert sturdy timbers or steels through the holes and support on acrow props either side. Then you can knock out the opening for the lintels. Bed lintels and pack up above them. Once the lintels are in and gone off, take out window opening. Angle grind all the openings first as deep as possible to make clean cuts. With random stone though you will come across boulders that will have to come out and holes that need to be made good.
However, to make life simpler, I´ve found that with walls that thick, you can address it from one side at at time i.e. from either the inside or the outside, take out enough wall to get one lintel in, then, once that one´s in and packed up, go round to the other side and take that out. Depends on the state of your walls and never leave an opening unsupported for any length of time.
Also, I´m sure you don´t need telling that this is structural work, not to be undertaken if you don´t know what you are doing and (technically) needs a major works licence plus architect.

Thats how my OH did it in all our openings and yes we had the major works licences.
He removed them from one side securing it and then from the other, he also used acro props.
We found alsorts in our stone wall including earth in the centre.
Good luck we are almost 2/3rd the way through our renovations, cant wait now for it to be finished.
Sharon

Takes me back to when I helped my dad do the same in a cottage my folks had in Devon which had random rubble walling.
After much head scratching we decided on the following as being the simplest way of tackling the job;
Having marked the position for the window we first cut through the wall above and inserted the props. This enabled us to remove the rubble below. Of course, due to the random nature of the wall material we finished up with an irregular hole.
To avoid the task of trying to achieve even surfaces both horizontally and vertically using stone, we first shuttered up the wall to the eventual sill level and concreted it . This gave us a flat surface to work with. We then built a plywood box on this the same size as the window was going to be, and shuttered each side up to the level of the top of the box. Concreting both sides in gave us two perfect vertical sides, and brought us up to lintel level. We then shuttered up on top of the box and cast the (reinforced ) lintel in-situ.
Once the concrete had gained about 75% of its ultimate strength - in about a week (I took some test cubes back to the lab to check, 35n/mm2! not bad for site mix - we removed the props and filled in the gap above, then finally removed the plywood box which left us with a perfectly formed space for the window. All that remained was to render the new concrete to match the existing wall. Hope this helps.