A modular bund system for forming a liquid impermeable bund, comprising: a plurality of wall members, each wall member comprising an upper portion and a foot portion extending from a lower edge of an outer face of the upper portion; and a plurality of angular connecting members, each angular connecting member configured to connect one of the plurality of wall members to another one of the plurality of wall members to form a corner of a bund, wherein each connecting member comprises: a central foot portion configured to be coplanar with the foot portions of the one and the another one of the plurality of wall members, and, upwards from the central foot portion, a central portion; a first flange and a second flange, each extending outwards, wherein the first flange is configured to overlap an end portion of the one of a plurality of wall members and the second flange is configured to overlap an end portion of the another one of the plurality of wall members; the modular bund system further comprises means for sealing each flange to the respective wall member end portion such that a liquid impermeable bund is formed; characterised in that each wall member has an L-shaped cross-sectional profile; and an inner surface of the central portion is configured to be coplanar with respective inner surfaces of the one and the another one of the plurality of wall members when the first flange and the second flange overlap the respective end portions of the said wall members. a plurality of wall members, each wall member comprising an upper portion and a foot portion extending from a lower edge of an outer face of the upper portion; and a plurality of angular connecting members, each angular connecting member configured to connect one of the plurality of wall members to another one of the plurality of wall members to form a corner of a bund, wherein each connecting member comprises: a central foot portion configured to be coplanar with the foot portions of the one and the another one of the plurality of wall members, and, upwards from the central foot portion, a central portion; a first flange and a second flange, each extending outwards, wherein the first flange is configured to overlap an end portion of the one of a plurality of wall members and the second flange is configured to overlap an end portion of the another one of the plurality of wall members; the modular bund system further comprises means for sealing each flange to the respective wall member end portion such that a liquid impermeable bund is formed; characterised in that each wall member has an L-shaped cross-sectional profile; and an inner surface of the central portion is configured to be coplanar with respective inner surfaces of the one and the another one of the plurality of wall members when the first flange and the second flange overlap the respective end portions of the said wall members. a central foot portion configured to be coplanar with the foot portions of the one and the another one of the plurality of wall members, and, upwards from the central foot portion, a central portion; a first flange and a second flange, each extending outwards, wherein the first flange is configured to overlap an end portion of the one of a plurality of wall members and the second flange is configured to overlap an end portion of the another one of the plurality of wall members; the modular bund system further comprises means for sealing each flange to the respective wall member end portion such that a liquid impermeable bund is formed; characterised in that each wall member has an L-shaped cross-sectional profile; and an inner surface of the central portion is configured to be coplanar with respective inner surfaces of the one and the another one of the plurality of wall members when the first flange and the second flange overlap the respective end portions of the said wall members.