Why Italy's Trieste does not simply restart British amphibious construction

Does the commissioning of Italy's Trieste create pressure for Britain to build two more large aviation or amphibious ships after the Type 26 program?

Not directly, because Trieste is an LHD and Britain would build that type in different yards from the frigate line; the larger constraint is preserving specialized industrial capacity and a workable deployment-refit cycle.

The Type 26 yard is organized as a frigate factory and is more likely to continue with major escorts than switch to an LHD. A British amphibious aviation ship would instead draw on yards such as Cammell Laird, Harland & Wolff, or Rosyth, depending on the design and construction strategy. Rosyth also supports the Queen Elizabeth-class carrier program, so new work must not disrupt the facilities needed for carrier refits. Operating only two large aviation ships tends to leave one deployed while the other undergoes deep maintenance, a cycle already familiar from the two-ship LPD force and less resilient than a three-hull rotation.