Even a one-sentence email would be great, simply urging the Mayor to reject the application.
If you want to write a couple of sentence, you could also...
- Remind him that he has pledged to veto tower block plans that don't fit in to the local context (i.e. central Walthamstow's character is largely two- and three-storey, much of it Victorian).
- And point out that architecture experts CABE recommended that the plans be rejected because the blocks on either side of the station are still too tall to meet the council's own planning policy, and because the architectural quality of the main 14-storey hotel tower block still isn't good enough.