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Apparatus which can collect loose debris, particularly ferrous debris, has a body 2 with upper 3 and lower 4 stabiliser sleeve. The body 2 has a one or more integral magnets or magnetic areas 5. In one embodiment the magnets are located in a first and second row on a split sleeve 6 and are covered b

Apparatus which can collect loose debris, particularly ferrous debris, has a body 2 with upper 3 and lower 4 stabiliser sleeve. The body 2 has a one or more integral magnets or magnetic areas 5. In one embodiment the magnets are located in a first and second row on a split sleeve 6 and are covered by a protective stainless steel sleeve7. The apparatus may alternatively comprise magnetic scraper blades or a magnetic sub. The magnets are selectively activated. There is also described a method of trapping or retaining debris in a well bore.

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1. Apparatus for collecting loose debris or particles in a well casing or liner, the apparatus comprising a body for attachment to a work string, the body including an upper and lower stabiliser, one or more magnets supported between the stabilisers and a protective sleeve positioned over the magnet

1. Apparatus for collecting loose debris or particles in a well casing or liner, the apparatus comprising a body for attachment to a work string, the body including an upper and lower stabiliser, one or more magnets supported between the stabilisers and a protective sleeve positioned over the magnets, wherein the protective sleeve is free to rotate relative to the stabilisers. 2. Apparatus as claimed in claim 1, wherein the stabilisers are non-rotating spiral stabilisers. 3. Apparatus as claimed in claim 1, wherein the magnets are permanent magnets. 4. Apparatus as claimed in claim 1, wherein the magnets are changeable between an inactivated mode where a magnetic field which attracts loose debris is off and an activated mode where the magnetic field is on. 5. Apparatus as claimed in claim 1, wherein the magnets are arranged on a split sleeve comprising a first and a second row of magnets. 6. Apparatus as claimed in claim 5 wherein the are selectively activated and deactivated by virtue of moving a first row of magnets relative to a second row of magnets. 7. Apparatus as claimed in claim 1, wherein the apparatus has integral cleaning members on the body of the tool, located above the one or more magnets. 8. Apparatus as claimed in claim 7, wherein the cleaning members are casing scrapers. 9. Apparatus as claimed in claim 7, wherein the cleaning members are brushes. 10. A method of collecting loose debris or particles in a well casing or liner, the method comprising the steps of: (a) attaching to a work string, apparatus comprising a body including an upper and lower stabiliser, one or more magnets supported between the stabilisers and a protective sleeve positioned over the magnets which is free to rotate relative to the stabilisers; (b) running the apparatus into the well casing or liner; (c) attracting and retaining said debris and particles on the protective sleeve; and (d) removing the apparatus from the well casing or liner in order to remove the debris and particles. 11. A method as claimed in claim 10 further comprising the steps of: (a) deactivating the one or more magnets prior to running the apparatus; and (b) activating the one or more magnets when the apparatus is in the well casing or liner to create a magnetic field to attract and retain said debris and particles.