Technique for constraining access to memory using capabilities

An apparatus and method for constraining access to memory using capabilities. Processing circuitry performs operations during which access requests to memory are generated, with memory addresses for the access requests being generated using capabilities that identify constraining information. Capability checking circuitry performs a capability check operation to determine whether a given access request whose memory address is generated using a given capability is permitted based on the constraining information. Memory access checking circuitry then further constrains access to the memory by the given access request in dependence on a level of trust. The given capability has a capability level of trust associated therewith, and the level of trust associated with the given access request is dependent on both the current mode level of trust associated with the current mode of operation of the processing circuitry, and the capability level of trust of the given capability.