Hi there everyone, I'm hoping someone might be able to help.

I'm worried that my pretty lemon tree is dying. I have had it for over a year after it was given as a present to my mum from my other half, and thought I did a good job keeping it in great condition. Its about a foot and a half tall and the variety is a Four Seasons Lemon, and its currently living in London, UK.

The first winter and summer went by quite well, with it sitting on a south-facing window sill. I gave it feed ever so often and the plant seemed brilliantly healthy, giving one or two fruits and lots of bloom. It grew rapidly in the summer, and I cut back a very unbalanced long shoot. I also repotted it into a large ornate ceramic pot, using citrus compost. (I've read about 'drainage', but haven't fully understood whether its essential - my new pot has no holes at the bottom). It received a lot of good light in the summer, but towards the end, it started to drop its leaves and all the small fruit that had started to set.

Since then, as its too big for the window sill, I moved it to a table on the other side of the house, which has only some light, and is about 2 metres away from a radiator. My research has found that changes in environment means that the plant can drop its leaves, so I didn't panic. But at this stage, every leaf has dropped off the plant and all the tips of the branches are starting to brown. I'm worried that its something serious. There is one lemon left on it, about the size of a large lime. I water it only when it becomes quite dry, and the leaves haven't shown signs of strain before.

Sorry to have made this so long, but if anyone knows what it could be, I'd be very grateful for suggestions. On a final note, my other half said that if the lemon plant dies, then I will too, so I'm starting to get a bit desperate..

Thanks in advance!