An actuation system comprising: a tubular defining a passage; and an assembly disposed with the tubular, the assembly including a restriction operatively arranged to receive a restrictor for enabling actuation of the assembly, the restriction including a degradable material with a protective layer thereon, the degradable material degrading upon exposure to a fluid in the passage and the protective layer isolating the degradable material from the fluid, the degradable material including an uncovered area with respect to the protective layer; characterised in that: the assembly includes a sleeve disposed between the restriction and the tubular and a channel that extends from the uncovered area through the sleeve; wherein, when the restrictor is received by the restriction, the restrictor blocks fluid flow through the passage so that the sleeve can be actuated by creating a pressure differential across the restrictor; and wherein actuation of the sleeve establishes fluid communication between the uncovered area and the passage, wherein fluid communication between the uncovered area and the passage is enabled by a cavity in the tubular together with the channel wherein the cavity is misaligned with the uncovered area before actuation and the cavity is aligned with the uncovered area after actuation. a tubular defining a passage; and an assembly disposed with the tubular, the assembly including a restriction operatively arranged to receive a restrictor for enabling actuation of the assembly, the restriction including a degradable material with a protective layer thereon, the degradable material degrading upon exposure to a fluid in the passage and the protective layer isolating the degradable material from the fluid, the degradable material including an uncovered area with respect to the protective layer; characterised in that: the assembly includes a sleeve disposed between the restriction and the tubular and a channel that extends from the uncovered area through the sleeve; wherein, when the restrictor is received by the restriction, the restrictor blocks fluid flow through the passage so that the sleeve can be actuated by creating a pressure differential across the restrictor; and wherein actuation of the sleeve establishes fluid communication between the uncovered area and the passage, wherein fluid communication between the uncovered area and the passage is enabled by a cavity in the tubular together with the channel wherein the cavity is misaligned with the uncovered area before actuation and the cavity is aligned with the uncovered area after actuation. the assembly includes a sleeve disposed between the restriction and the tubular and a channel that extends from the uncovered area through the sleeve; wherein, when the restrictor is received by the restriction, the restrictor blocks fluid flow through the passage so that the sleeve can be actuated by creating a pressure differential across the restrictor; and wherein actuation of the sleeve establishes fluid communication between the uncovered area and the passage, wherein fluid communication between the uncovered area and the passage is enabled by a cavity in the tubular together with the channel wherein the cavity is misaligned with the uncovered area before actuation and the cavity is aligned with the uncovered area after actuation.