Downhole slip apparatus

A method of operating a downhole slip apparatus, the downhole slip apparatus comprising a radially extendable slip assembly comprising a primary slip defining a first wall engaging surface, a secondary slip defining a second wall engaging surface, and a selective coupling or clutch, the clutch or selective coupling being configured or operable such that during a first phase of operation the primary and secondary slips are radially extendable simultaneously from a retracted configuration towards and/or into a first extended configuration, and during a subsequent second phase of operation the secondary slip is radially extendable relative to the primary slip towards and/or into a second extended configuration,

• wherein the first and second wall engaging surfaces comprise piercing features and interference features, wherein the downhole slip apparatus comprises or is configured to receive a slip actuator, wherein the method comprises:
• operating the slip actuator such that, during the first phase of operation, the primary and secondary slips are radially extended simultaneously from the retracted configuration towards and/or into the first extended configuration;
• operating or reconfiguring the clutch or selective coupling;
• and
• operating the slip actuator such that, during the subsequent second phase of operation, the secondary slip radially extends relative to the primary slip towards and/or into the second extended configuration.