Good to see some others wanting to make a change.
Take a look at my fitness thread and a few of the others as there has been quite a bit of useful info from researching and people contributing in there.
A few things that generally have been helping me;
1. Minimal carbs after lunch. Veg, protein (fish, meat, bean curd, cottage cheese, eggs etc) are preferable. Fruits are ok but do have carbs for the most part.
2. Cut down on portion size. Think 'Go regular rather than upsize.'
3. Keep a food log till you get an idea of what the food you are eating is made up of and can balance your percentages for fat, protein and carbs.
4. Keep a journal here or some other site with progress pictures as these are likely to be one of the strongest motivators.
If you are set on looking for a Ketosis diet (minimal to zero carbs) then take a look at the CKD diet as it allows you to load on carbs in a cyclic way so you do not completely starve the body of them. It is meant to be less uncomfortable and easier to maintain although from the research I did, Ketosis based diets are not recommended for any long term lifestyle change. Shed some weight then get on to a maintaining diet.
Exercise will be difficult for a bit due to the extra weight you have and the strain it is putting on your frame and organs.
You don't list where abouts you are but is doing some rambling a possibility through forests, gentle hills. The soft ground should make it easier on the joints as long as you watch your step.
Another option may be what I am doing and very much enjoy. Get a big punch bag and some boxing gloves and work out any frustration. I find running machines or exercise bikes etc pretty boring but working the punch bag I love. Go gentle at first and work up to it.
The biggest factor, I think, is getting to right games plan and understanding that this 10 stone loss must be a long term goal. 10 stone is 140lbs ( around 63.5kg). Loosing at the recommended max of 2lbs per week you are still looking at 70 weeks or 2 years. Loosing too fast and you run the risk of floppy skin and hitting health problems.
Now that is the bad news.
Here is the good news...
1. It took 6 years to put on and with determination and hard work you could get it off in just over 2. Taking in to account injury, holidays, the occasional slip here and there, maybe aim for 2.5 years.
2. There are lots of supportive and knowledgeable people here who are happy to help if you make the effort. They will also point the finger if you are not

.
3. The first picture you take for your journal will be one of your biggest motivators. Use it. Put it everywhere, the fridge, the kitchen doors so any time you have temptation for a chocolate bar or some other treat it will hopefully give you pause for thought. Keep one in your wallet for when you go out. As time goes on, only leave it in the places you are most likely to have temptation like the fridge. Put the current photo underneath it so you can see the difference as a reinforcement for the effects of the changes you have made.
4. Have a look at the
EXRX.net exercise directory for a list of exercises and short videos of the correct form.
5. Read the threads here for workout suggestions. There are a few in my
thread starting with a simple full body compound routine to build starting strength. Remember to go slow to start. The muscles will adapt quite fast but the ligaments will take more time and you really do not want to have to stop as you have pushed it to far too fast.
6. As you get fitter and drop the weight you will feel fitter, freer, less self concious. Your body will thank you for it, your wife will hopefully thank you for it as will your children / grandchildren.
7. You are not the only one around this age starting off trying to correct letting yourself go in the past. Not all of us are in our 20s, I know I am not

and although it is a little harder starting later it is no where near impossible.
8. The best bit. The hardest part is over as you have already started

.
Keep us all updated.
Good luck
RB