Downhole method for separating well tubular structure

A downhole method for preparing and/or providing isolation at a predetermined position in an existing well having a top and a first well tubular metal structure arranged in a wellbore, the first well tubular metal structure having a longitudinal extension, comprising:

• inserting a downhole tool comprising a bit on a projection part in the first well tubular metal structure,
• positioning the downhole tool at the predetermined position,
• separating a first section being an upper part of the first well tubular metal structure from a second section being a lower part of the first well tubular metal structure by machining into and along a circumference of the first well tubular metal structure,
• moving the downhole tool a predetermined distance upwards along the longitudinal extension in the first section of the first well tubular metal structure to a second position above the predetermined position, and
• separating a first part of the first section of the first well tubular metal structure from a second part of the first section of the first well tubular metal structure by machining into and along a circumference of the first well tubular metal structure, providing an uncased opening between the second part of the first section and the second section.