Sick pay and ESA

Contribution-based ESA can be claimed after 28 weeks of SSP. Can a civil servant (or anyone employee) entitled to 6 months sick leave on full pay followed by 6 months on half pay claim ESA after 28 weeks, so getting both contractual sick pay and ESA at the same time, and with no reduction in the ESA (as would have happened if in receipt of an occupational pension, for example)? Does it make any difference whether the contract of employment describes what he is getting as sick pay or not?

Yes to the first question and no to the second.  Some employers will reduce the contractual payments by the amount of ESA, some will only do that for high earners and some won’t reduce at all.