Low level hammering noise in Winterwell rd

[dadalr]

Has been going on for months but past few weeks got much louder.
Very regular Mon to Fri 8.45am to 4pm, its constantly going on with hardly any pause.
Only audible inside
No building site nearby
Any idea what it may be?
Thanks

 

[teuchter]

London Power Tunnels ?

 

[dadalr]

Thanks called their community relations helpline and waiting for a call back.