Broken top of old rainwater drain hopper

I moved into my 1937-built semi-detached house two years ago. I detect an intermittent smell in my front room which shares a party wall with neighbour. Outside on the boundary there is a drain originally serving a downpipe from a valley gutter between our two pitched roofs. 3 or 4 years ago the neighbour (absentee landlord with 6 student tenants) added an extension at the front with a new kitchen. The earthenware hopper now serves three pipes: original downpipe, the outlet from the kitchen and one from another new rainwater downpipe.
I went out after dark and examined the hopper. The rim is broken, the discharge pipe from the sink ends above the drain, and half the water splashes on the edge of the hopper, and enters a void behind the broken top of the hopper. I enclose a link to photos.

Stivulya / Стивуля

1. If I mend top, concrete round, extend pipes, is that sufficient? Drain appears to drain normally.
2. Is it legal / good practice to drain kitchen discharge and extra rainwater downpipe into pipe originally intended for rainwater?
3. Presumably the drain is joint responsibility of me and neighbour?

 

2. Depends where you are and if the foul and surface water sewers are common. If not common, then surface water (gutters) should drain into one set of drains, and foul water (sinks, basins, baths, showers, toilets) should drain into the foul sewage system. Draining foul waste into surface water drains is illegal. Surface water into foul water drains is also wrong, but causes less damage.

1. Subject to 2. above, probably OK

3. Probably joint. Presumably he asked and received permission from the previous owners before building the extension and altering the drainage?

Needs attention fairly urgently, as leakage can wash under the foundations.

Its not really a hopper, but a gully.

 

Thanx for prompt reply steadyon & providing "gully". I had an online chat with someone from Severn Trent yesterday. He wrote:

"I've checked your address and I can't see any of our sewers inside your property boundary, it is possible that the pipes are ours just not mapped."

"With the pipes the rain water pipes in the garden will not be shown on our system."

How can pipes not be mapped?
How would I find out whether it's combined or separate. Would a plumber be able to tell? Would a (previously council) house this age be most likely combined?
I'm in slightly difficult position. Landlord not local. His dad - Chinese chap with limited English - said smell in my front room was just mould, even tho has sewer smell - and added that the floor next door slopes very slightly! Poss due to this going on for years? I can see void outside the gully, poss due to water wearing a channel.

 

Btw - bloke from ST said can't tell me any details of extension permits due to data protection reasons.