In an embodiment, the present invention provides a pressure containment device which includes a housing with a returns outlet port, an injection port, and an overflow outlet port, and a seal assembly with a seal arranged in the housing to surround and enter into a sealing engagement with a tubular body extending along a passage in the housing via a sealing face. The injection port is arranged between the returns outlet port and a first end of the seal. The overflow outlet port is arranged adjacent to a second, opposite, end of the seal and communicates with an upper end of the passage. The upper end of the passage connects to a bell nipple or to a section of a riser pipe and, in use, the overflow outlet port is exposed to a hydrostatic head provided by a fluid in the bell nipple or the section of the riser pipe.