Firstly, to the extent that any of the lump sum relates to statutory redundancy, that element is entirely ignored for tax purposes.
After the statutory sum, he will have the "ex gratia" payment. As he has such long service, he'll get about 40k of that tax free (presuming he qualifies for and claims the increased exemption). The remainder will be taxed at 43% (41% income tax and 2% health levies).
Alternatively, there is another calculation that can be used call the SCSB and it is often of benefit where a person has long service (as in this case). To calculate the tax free lump sum under the SCSB, you take the average earnings for the last three years, multiply it by the number of full years of service and divide by 15. This figure is then reduced by the lump sum he is entitled to from his pension scheme (if any and he can opt to waive the lump sum).
Again, the balance of the lump sum is subject to tax at 43%. However, at the end of the year, he should be able to reclaim some of the tax on this using what is called "top slicing relief".
The revenue leaflet ([broken link removed]) should help him understand the tax aspects.